5. Surface Anatomy of the Thorax

Bones.—The skeleton of the thorax is to a very considerable extent covered by muscles, so that in the strongly developed muscular subject it is for the most part concealed. In the emaciated subject, however, the ribs, especially in the lower and lateral regions, stand out as prominent ridges with the sunken intercostal spaces between them. 1
In the middle line, in front, the superficial surface of the sternum can be felt throughout its entire length at the bottom of a furrow, the sternal furrow, situated between the Pectorales majores. These muscles overlap the anterior surface somewhat, so that the whole width of the sternum is not subcutaneous, and this overlapping is greatest opposite the middle of the bone; the furrow, therefore, is wide at its upper and lower parts but narrow in the middle. At the upper border of the manubrium sterni is the jugular notch: the lateral parts of this notch are obscured by the tendinous origins of the Sternocleidomastoidei, which appear as oblique cords narrowing and deepening the notch. Lower down on the subcutaneous surface is a well-defined transverse ridge, the sternal angle; it denotes the junction of the manubrium and body. From the middle of the sternum the sternal furrow spreads out and ends at the junction of the body with the xiphoid process. Immediately below this is the infrasternal notch; between the sternal ends of the seventh costal cartilages, and below the notch, is a triangular depression, the epigastric fossa, in which the xiphoid process can be felt. 2
On either side of the sternum the costal cartilages and ribs on the front of the thorax are partly obscured by the Pectoralis major, through which, however, they can be felt as ridges with yielding intervals between them corresponding to the intercostal spaces. Of these spaces, that between the second and third ribs is the widest, the next two are somewhat narrower, and the remainder, with the exception of the last two, are comparatively narrow. 3
Below the lower border of the Pectoralis major on the front of the chest, the broad flat outlines of the ribs as they descend, and the more rounded outlines of the costal cartilages, are often visible. The lower boundary of the front of the thorax, which is most plainly seen by bending the body backward, is formed by the xiphoid process, the cartilages of the seventh, eighth, ninth, and tenth ribs, and the ends of the cartilages of the eleventh and twelfth ribs. 4
On either side of the thorax, from the axilla downward, the flattened external surfaces of the ribs may be defined. Although covered by muscles, all the ribs, with the exception of the first, can generally be followed without difficulty over the front and sides of the thorax. The first rib being almost completely covered by the clavicle can only be distinguished in a small portion of its extent. 5
At the back, the angles of the ribs lie on a slightly marked oblique line on either side of, and some distance from, the spinous processes of the vertebræ. The line diverges somewhat as it descends, and lateral to it is a broad convex surface caused by the projection of the ribs beyond their angles. Over this surface, except where covered by the scapula, the individual ribs can be distinguished. 6

Muscles.—The surface muscles covering the thorax belong to the musculature of the upper extremity (Figs. 1215, 1219), and will be described in that section (page 1325). There is, however, an area of practical importance bounded by these muscles. It is limited above by the lower border of Trapezius, below by the upper border of Latissimus dorsi, and laterally by the vertebral border of the scapula; the floor is partly formed by Rhomboideus major. If the scapula be drawn forward by folding the arms across the chest, and the trunk bent forward, parts of the sixth and seventh ribs and the interspace between them become subcutaneous and available for ausculation. The space is therefore known as the triangle of ausculation. 7

FIG. 1215– The left side of the thorax. (See enlarged image)

Mamma.—The size of the mamma is subject to great variations. In the adult nulliparous female, it extends vertically from the second to the sixth rib, and transversely from the side of the sternum to the midaxillary line. In the male and in the nulliparous female the mammary papilla is situated in the fourth interspace about 9 or 10 cm. from the middle line, or 2 cm. from the costochondral junction. 8

6. Surface Markings of the Thorax

Bony Landmarks.—The second costal cartilage corresponding to the sternal angle is so readily found that it is used as a starting-point from which to count the ribs. The lower border of the Pectoralis major at its attachment corresponds to the fifth rib; the uppermost visible digitation of Serratus anterior indicates the sixth rib. 1
The jugular notch is in the same horizontal plane as the lower border of the body of the second thoracic vertebra; the sternal angle is at the level of the fifth thoracic vertebra, while the junction between the body and xiphoid process of the sternum corresponds to the fibrocartilage between the ninth and tenth thoracic vertebræ. 2
The influence of the obliquity of the ribs on horizontal levels in the thorax is well shown by the following line. “If a horizontal line be drawn around the body at the level of the inferior angle of the scapula, while the arms are at the sides, the line would cut the sternum in front between the fourth and fifth ribs, the fifth rib in the nipple line, and the ninth rib at the vertebral column.” (Treves). 3

Diaphragm.—The shape and variations of the diaphragm as seen by skiagraphy have already been described (page 407). 4

Surface Lines.—For clinical purposes, and for convenience of description, the surface of the thorax has been mapped out by arbitrary lines (Fig. 1220). On the front of the thorax the most important vertical lines are the midsternal, the middle line of the sternum; and the mammary, or, better midclavicular, which runs vertically downward from a point midway between the center of the jugular notch and the tip of the acromion. This latter line, if prolonged, is practically continuous with the lateral line on the front of the abdomen. Other vertical lines on the front of the thorax are the lateral sternal along the sternal margin, and the parasternal midway between the lateral sternal and the mammary. 5
On either side of the thorax the anterior and posterior axillary lines are drawn vertically from the corresponding axillary folds; the midaxillary line runs downward from the apex of the axilla. 6
On the posterior surface of the thorax the scapular line is drawn vertically through the inferior angle of the scapula. 7

FIG. 1216– Front of thorax, showing surface relations of bones, lungs (purple), pleura (blue), and heart (red outline). P. Pulmonary valve. A. Aortic valve. B. Bicuspid valve. T. Tricuspid valve. (See enlarged image)

Pleuræ (Figs. 1216, 1217).—The lines of reflection of the pleuræ can be indicated on the surface. On the right side the line begins at the sternoclavicular articulation and runs downward and medialward to the midpoint of the junction between the manubrium and body of the sternum. It then follows the midsternal line to the lower end of the body of the sternum or on to the xiphoid process, where it turns lateralward and downward across the seventh sternocostal articulation. It crosses the eighth costochondral junction in the mammary line, the tenth rib in the midaxillary line, and is prolonged thence to the spinous process of the twelfth thoracic vertebra. 8
On the left side, beginning at the sternoclavicular articulation, it reaches the midpoint of the junction between the manubrium and body of the sternum and extends down the midsternal line in contact with that of the opposite side to the level of the fourth costal cartilage. It then diverges lateralward and is continued downward slightly lateral to the sternal border, as far as the sixth costal cartilage. Running downward and lateralward from this point it crosses the seventh costal cartilage, and from this onward it is similar to the line on the right side, but at a slightly lower level. 9

Lungs (Figs. 1216, 1217).—The apex of the lung is situated in the neck above the medial third of the clavicle. The height to which it rises above the clavicle varies very considerably, but is generally about 2.5 cm. It may, however, extend as high as 4 or 5 cm., or, on the other hand, may scarcely project above the level of this bone. 10

FIG. 1217– Side of thorax, showing surface markings for bones, lungs (purple), pleura (blue), and spleen (green). (See enlarged image)

In order to mark out the anterior borders of the lungs a line is drawn from each apex point—2.5 cm. above the clavicle and rather nearer the anterior than the posterior border of Sternocleidomastoideus—downward and medialward across the sternoclavicular articulation and manubrium sterni until it meets, or almost meets, its fellow of the other side at the midpoint of the junction between the manubrium and body of the sternum. From this point the two lines run downward, practically along the midsternal line, as far as the level of the fourth costal cartilages. The continuation of the anterior border of the right lung is marked by a prolongation of its line vertically downward to the level of the sixth costal cartilage, and then it turns lateralward and downward. The line on the left side curves lateralward and downward across the fourth sternocostal articulation to reach the parasternal line at the fifth costal cartilage, and then turns medialward and downward to the sixth sternocostal articulation. 11
In the position of expiration the lower border of the lung may be marked by a slightly curved line with its convexity downward, from the sixth sternocostal junction to the tenth thoracic spinous process. This line crosses the mid-clavicular line at the sixth, and the midaxillary line at the eighth rib. 12
The posterior borders of the lungs are indicated by lines drawn from the level of the spinous process of the seventh cervical vertebra, down either side of the vertebral column, across the costovertebral joints, as low as the spinous process of the tenth thoracic vertebra. 13
The position of the oblique fissure in either lung can be shown by a line drawn from the spinous process of the second thoracic vertebra around the side of the thorax to the sixth rib in the mid-clavicular line; this line corresponds roughly to the line of the vertebral border of the scapula when the hand is placed on the top of the head. The horizontal fissure in the right lung is indicated by a line drawn from the midpoint of the preceding, or from the point where it cuts the midaxillary line, to the midsternal line at the level of the fourth costal cartilage. 14

Trachea.—This may be marked out on the back by a line from the spinous process of the sixth cervical to that of the fourth thoracic vertebra where it bifurcates; from its bifurcation the two bronchi are directed downward and lateralward. In front, the point of bifurcation corresponds to the sternal angle. 15

Esophagus.—The extent of the esophagus may be indicated on the back by a line from the sixth cervical to the level of the ninth thoracic spinous process, 2.5 cm. to the left of the middle line. 16

Heart.—The outline of the heart in relation to the front of the thorax (Figs 1216, 1218) can be represented by a quadrangular figure. The apex of the heart is first determined, either by its pulsation or as a point in the fifth interspace, 9 cm. to the left of the midsternal line. The other three points are: (a) the seventh right sternocostal articulation; (b) a point on the upper border of the third right costal cartilage 1 cm. from the right lateral sternal line; (c) a point on the lower border of the second left costal cartilage 2.5 cm. from the left lateral sternal line. A line joining the apex to point (a) and traversing the junction of the body of the sternum with the xiphoid process represents the lowest limit of the heart—its acute margin. The right and left borders are represented respectively by lines joining (a) to (b) and the apex to (c); both lines are convex lateralward, but the convexity is more marked on the right where its summit is 4 cm. distant from the midsternal line opposite the fourth costal cartilage. 17
A portion of the area of the heart thus mapped out is uncovered by lung, and therefore gives a dull note on percussion; the remainder being overlapped by lung gives a more or less resonant note. The former is known as the area of superficial cardiac dulness, the latter as the area of deep cardiac dulness. The area of superficial cardiac dulness is somewhat triangular; from the apex of the heart two lines are drawn to the midsternal line, one to the level of the fourth costal cartilage, the other to the junction between the body and xiphoid process; the portion of the midsternal line between these points is the base of the triangle. Latham lays down the following rule as a sufficient practical guide for the definition of the area of superficial dulness. “Make a circle of two inches in diameter around a point midway between the nipple and the end of the sternum.” 18
The coronary sulcus can be indicated by a line from the third left, to the sixth right, sternocostal joint. The anterior longitudinal sulcus is a finger’s breadth to the right of the left margin of the heart. 19
The position of the various orifices is as follows: The pulmonary orifice is situated in the upper angle of the third left sternocostal articulation; the aortic orifice is a little below and medial to this, close to the articulation. The left atrioventricular opening is opposite the fourth costal cartilage, and rather to the left of the midsternal line; the right atrioventricular opening is a little lower, opposite the fourth interspace of the right side. The lines indicating the atrioventricular openings are slightly below and parallel to the line of the coronary sulcus. 20

Arteries.—The line of the ascending aorta begins slightly to the left of the midsternal line opposite the third costal cartilage and extends upward and to the right to the upper border of the second right costal cartilage. The beginning of the aortic arch is indicated by a line from this latter point to the midsternal line about 2.5 cm. below the jugular notch. The point on the midsternal line is opposite the summit of the arch, and a line from it to the right sternoclavicular articulation represents the site of the innominate artery, while another line from a point slightly to the left of it and passing through the left sternoclavicular articulation indicates the position of the left common carotid artery in the thorax. 21

FIG. 1218– Diagram showing relations of opened heart to front of thoracic wall. Ant. Anterior segment of tricuspid valve. A O. Aorta. A.P. Anterior papillary muscle. In. Innominate artery. L.C.C. Left common carotid artery. L.S. Left subclavian artery. L.V. Left ventricle. P.A. Pulmonary artery. R.A. Right atrium. R.V. Right ventricle. V.S. Ventricular septum. (See enlarged image)

The internal mammary artery descends behind the first six costal cartilages about 1 cm. from the lateral sternal line. 22

Veins.—The line of the right innominate vein crosses the right sternoclavicular joint and the upper border of the first right costal cartilage about 1 cm. from the lateral sternal line; that of the left innominate vein extends from the left sternoclavicular articulation to meet the right at the upper border of the first right costal cartilage. The junction of the two lines indicates the origin of the superior vena cava, the line of which is continued vertically down to the level of the third right costal cartilage. The end of the inferior vena cava is situated opposite the upper margin of the sixth right costal cartilage about 2 cm. from the midsternal line. 23

Henry Gray (1821–1865). Anatomy of the Human Body. 1918.

7. Surface Anatomy of the Abdomen

Skin.—The skin of the front of the abdomen is thin. In the male it is often thickly hair-clad, especially toward the lower part of the middle line; in the female the hairs are confined to the pubes. Just below the line of the iliac crest, especially marked in fat subjects, is a shallow groove termed the iliac furrow, while in the site of the inguinal ligament a sharper fold known as the fold of the groin is easily distinguishable. 1
After distension of the abdomen from pregnancy or other causes the skin commonly presents transverse white lines which are quite smooth, being destitute of papillæ; these are known as striæ gravidarum or striæ albicantes. The linea nigra of pregnancy is often seen as a pigmented brown streak in the middle line between the umbilicus and symphysis pubis. 2
In the middle line of the front of the abdomen is a shallow furrow which extends from the junction between the body of the sternum with the xiphoid process to a short distance below the umbilicus; it corresponds to the linea alba. The umbilicus is situated in the middle line, but it varies in position as regards its height; in an adult subject it is always placed above the middle point of the body, and in a normal well-nourished subject is from 2 to 2.5 cm. above the level of the tubercles of the iliac crests. 3

Bones.—The bones in relation with the surface of the abdomen are (1) the lower part of the vertebral column and the lower ribs and (2) the pelvis; the former have already been described (page 1303), the latter will be considered with the lower limb. 4

Muscles (Fig. 1219).—The only muscles of the abdomen which have any considerable influence on surface form are the Obliquus externus and the Rectus. The upper digitations of origin of Obliquus externus are well-marked in a muscular subject, interdigitating with those of Serratus anterior; the lower digitations are covered by the border of Latissimus dorsi and are not visible. The attachment of the Obliqui externus and internus to the crest of the ilium forms a thick oblique roll which determines the iliac furrow. Sometimes on the front of the lateral region of the abdomen an undulating line marks the passing of the muscular fibers of the Obliquus externus into its aponeurosis. The lateral margin of the Obliquus externus is separated from that of the Latissimus dorsi by a small triangular interval—the lumbar triangle—the base of which is formed by the iliac crest, and its floor by Obliquus internus. 5
The lateral margin of Rectus abdominis is indicated by the linea semilunaris, which may be exactly defined by putting the muscle into action. The surface of the Rectus presents three transverse furrows, the tendinous inscriptions: the upper two of these, viz., one opposite, or a little below, the tip of the xiphoid process, and the other midway between this point and the umbilicus, are usually well-marked; the third, opposite the umbilicus, is not so distinct. Between the two Recti the linea alba can be palpated from the xiphoid process to a point just below the umbilicus; it is represented by a distinct dip between the muscles: beyond this the muscles are in apposition. 6

Vessels.—In thin subjects the pulsation of the abdominal aorta can be readily felt by making deep pressure in the middle line above the umbilicus. 7

Viscera.—Under normal conditions the various portions of the digestive tube cannot be identified by simple palpation. Peristalsis of the coils of small intestine can be observed in some persons with extremely thin abdominal walls when some degree of constipation exists. In cases of constipation it is sometimes possible to trace portions of the great intestine by feeling the fecal masses within the gut. In thin persons with relaxed abdominal walls the iliac colon can be felt in the left iliac region—rolling under the fingers when empty and forming a distinct tumor when distended. 8

FIG. 1219– Surface anatomy of the front of the thorax and abdomen. (See enlarged image)

The greater part of the liver lies under cover of the lower ribs and their cartilages, but in the epigastric fossa it comes in contact with the abdominal wall. The position of the liver varies according to the posture of the body. In the erect posture in the adult male the edge of the liver projects about 1 cm. below the lower margin of the right costal cartilages, and its inferior margin can often be felt in this situation if the abdominal wall is thin. In the supine position the liver recedes above the margin of the ribs and cannot then be detected by the finger; in the prone position it falls forward and is then generally palpable in a patient with loose and lax abdominal walls. Its position varies with the respiratory movements; during a deep inspiration it descends below the ribs; in expiration it is raised. Pressure from without, as in tight lacing, by compressing the lower part of the chest, displaces the liver considerably, its anterior edge frequently extending as low as the crest of the ilium. Again its position varies greatly with the state of the stomach and intestines; when these are empty the liver descends, when they are distended it is pushed upward. 9
The pancreas can sometimes be felt, in emaciated subjects, when the stomach and colon are empty, by making deep pressure in the middle line about 7 or 8 cm. above the umbilicus. 10
The kidneys being situated at the back of the abdominal cavity and deeply placed cannot be palpated unless enlarged or misplaced. 11

7. Surface Anatomy of the Abdomen

Skin.—The skin of the front of the abdomen is thin. In the male it is often thickly hair-clad, especially toward the lower part of the middle line; in the female the hairs are confined to the pubes. Just below the line of the iliac crest, especially marked in fat subjects, is a shallow groove termed the iliac furrow, while in the site of the inguinal ligament a sharper fold known as the fold of the groin is easily distinguishable. 1
After distension of the abdomen from pregnancy or other causes the skin commonly presents transverse white lines which are quite smooth, being destitute of papillæ; these are known as striæ gravidarum or striæ albicantes. The linea nigra of pregnancy is often seen as a pigmented brown streak in the middle line between the umbilicus and symphysis pubis. 2
In the middle line of the front of the abdomen is a shallow furrow which extends from the junction between the body of the sternum with the xiphoid process to a short distance below the umbilicus; it corresponds to the linea alba. The umbilicus is situated in the middle line, but it varies in position as regards its height; in an adult subject it is always placed above the middle point of the body, and in a normal well-nourished subject is from 2 to 2.5 cm. above the level of the tubercles of the iliac crests. 3

Bones.—The bones in relation with the surface of the abdomen are (1) the lower part of the vertebral column and the lower ribs and (2) the pelvis; the former have already been described (page 1303), the latter will be considered with the lower limb. 4

Muscles (Fig. 1219).—The only muscles of the abdomen which have any considerable influence on surface form are the Obliquus externus and the Rectus. The upper digitations of origin of Obliquus externus are well-marked in a muscular subject, interdigitating with those of Serratus anterior; the lower digitations are covered by the border of Latissimus dorsi and are not visible. The attachment of the Obliqui externus and internus to the crest of the ilium forms a thick oblique roll which determines the iliac furrow. Sometimes on the front of the lateral region of the abdomen an undulating line marks the passing of the muscular fibers of the Obliquus externus into its aponeurosis. The lateral margin of the Obliquus externus is separated from that of the Latissimus dorsi by a small triangular interval—the lumbar triangle—the base of which is formed by the iliac crest, and its floor by Obliquus internus. 5
The lateral margin of Rectus abdominis is indicated by the linea semilunaris, which may be exactly defined by putting the muscle into action. The surface of the Rectus presents three transverse furrows, the tendinous inscriptions: the upper two of these, viz., one opposite, or a little below, the tip of the xiphoid process, and the other midway between this point and the umbilicus, are usually well-marked; the third, opposite the umbilicus, is not so distinct. Between the two Recti the linea alba can be palpated from the xiphoid process to a point just below the umbilicus; it is represented by a distinct dip between the muscles: beyond this the muscles are in apposition. 6

Vessels.—In thin subjects the pulsation of the abdominal aorta can be readily felt by making deep pressure in the middle line above the umbilicus. 7

Viscera.—Under normal conditions the various portions of the digestive tube cannot be identified by simple palpation. Peristalsis of the coils of small intestine can be observed in some persons with extremely thin abdominal walls when some degree of constipation exists. In cases of constipation it is sometimes possible to trace portions of the great intestine by feeling the fecal masses within the gut. In thin persons with relaxed abdominal walls the iliac colon can be felt in the left iliac region—rolling under the fingers when empty and forming a distinct tumor when distended. 8

FIG. 1219– Surface anatomy of the front of the thorax and abdomen. (See enlarged image)

The greater part of the liver lies under cover of the lower ribs and their cartilages, but in the epigastric fossa it comes in contact with the abdominal wall. The position of the liver varies according to the posture of the body. In the erect posture in the adult male the edge of the liver projects about 1 cm. below the lower margin of the right costal cartilages, and its inferior margin can often be felt in this situation if the abdominal wall is thin. In the supine position the liver recedes above the margin of the ribs and cannot then be detected by the finger; in the prone position it falls forward and is then generally palpable in a patient with loose and lax abdominal walls. Its position varies with the respiratory movements; during a deep inspiration it descends below the ribs; in expiration it is raised. Pressure from without, as in tight lacing, by compressing the lower part of the chest, displaces the liver considerably, its anterior edge frequently extending as low as the crest of the ilium. Again its position varies greatly with the state of the stomach and intestines; when these are empty the liver descends, when they are distended it is pushed upward. 9
The pancreas can sometimes be felt, in emaciated subjects, when the stomach and colon are empty, by making deep pressure in the middle line about 7 or 8 cm. above the umbilicus. 10
The kidneys being situated at the back of the abdominal cavity and deeply placed cannot be palpated unless enlarged or misplaced. 11

8. Surface Markings of the Abdomen

Bony Landmarks.—Above, the chief bony markings are the xiphoid process, the lower six costal cartilages, and the anterior ends of the lower six ribs. The junction between the body of the sternum and the xiphoid process is on the level of the tenth thoracic vertebra. Below, the main landmarks are the symphysis pubis and the pubic crest and tubercle, the anterior superior iliac spine, and the iliac crest. 1

Muscles (Fig. 1227).—The Rectus lies between the linea alba and the linea semilunaris; the former is indicated by the middle line, the latter by a curved line, convex lateralward, from the tip of the cartilage of the ninth rib to the public tubercle; at the level of the umbilicus the linea semilunaris is about 7 cm. from the middle line. The line indicating the junction of the muscular fibers of Obliquus externus with its aponeurosis extends from the tip of the ninth costal cartilage to a point just medial to the anterior superior iliac spine. 2
The umbilicus is at the level of the fibrocartilage between the third and fourth lumbar vertebræ. 3
The subcutaneous inguinal ring is situated 1 cm. above and lateral to the public tubercle; the abdominal inguinal ring lies 1 to 2 cm. above the middle of the inguinal ligament. The position of the inguinal canal is indicated by a line joining these two points. 4

Surface Lines.—For convenience of description of the viscera and of reference to morbid conditions of the contained parts, the abdomen is divided into nine regions, by imaginary planes, two horizontal and two sagittal, the edges of the planes being indicated by lines drawn on the surface of the body (Fig. 1220). In the older method the upper, or subcostal, horizontal line encircles the body at the level of the lowest points of the tenth costal cartilages; the lower, or intertubercular, is a line carried through the highest points of the iliac crests seen from the front, i. e., through the tubercles on the iliac crests about 5 cm. behind the anterior superior spines. An alternative method is that of Addison, who adopts the following lines: 5
(1) An upper transverse, the transpyloric, halfway between the jugular notch and the upper border of the symphysis pubis; this indicates the margin of the transpyloric plane, which in most cases cuts through the pylorus, the tips of the ninth costal cartilages and the lower border of the first lumbar vertebra; (2) a lower transverse line midway between the upper transverse and the upper border of the symphysis pubis; this is termed the transtubercular, since it practically corresponds to that passing through the iliac tubercles; behind, its plane cuts the body of the fifth lumbar vertebra. 6
By means of these horizontal planes the abdomen is divided into three zones named from above, the subcostal, umbilical, and hypogastric zones. Each of these is further subdivided into three regions by the two sagittal planes, which are indicated on the surface by a right and a left lateral line drawn vertically through points halfway between the anterior superior iliac spines and the middle line. The middle region of the upper zone is called the epigastric, and the two lateral regions the right and left hypochondriac. The central region of the middle zone is the umbilical, and the two lateral regions the right and left lumbar. The middle region of the lower zone is the hypogastric or pubic, and the lateral are the right and left iliac or inguinal. The middle regions, viz., epigastric, umbilical, and pubic, can each be divided into right and left portions by the middle line. In the following description of the viscera the regions marked out by Addison’s lines are those referred to. 7

FIG. 1220– Surface lines of the front of the thorax and abdomen. (See enlarged image)

Stomach (Fig. 1223).—The shape of the stomach is constantly undergoing alteration; it is affected by the particular phase of the process of gastric digestion, by the state of the surrounding viscera, and by the amount and character of its contents. Its position also varies with that of the body (Figs. 1221, 1222), so that it is impossible to indicate it on the surface with any degree of accuracy. The measurements given refer to a moderately filled stomach with the body in the supine position. 8

FIG. 1221– With the patient in the erect posture. (See enlarged image)

FIG. 1222– With the patient lying down. (See enlarged image)

FIG. 1223– Front of abdomen, showing surface markings for liver, stomach, and great intestine. (See enlarged image)

The cardiac orifice is opposite the seventh left costal cartilage about 2.5 cm. from the side of the sternum; it corresponds to the level of the tenth thoracic vertebra. The pyloric orifice is on the transpyloric line about 1 cm. to the right of the middle line, or alternately 5 cm. below the seventh right sternocostal articulation; it is at the level of the first lumbar vertebra. A curved line, convex downward and to the left, joining these points indicates the lesser curvature. In the left lateral line the fundus of the stomach reaches as high as the fifth interspace or the sixth costal cartilage, a little below the apex of the heart. To indicate the greater curvature a curved line is drawn from the cardiac orifice to the summit of the fundus, thence downward and to the left, finally turning medialward to the pyloric orifice, but passing, on its way, through the intersection of the left lateral with the transpyloric line. The portion of the stomach which is in contact with the abdominal wall can be represented roughly by a triangular area the base of which is formed by a line drawn from the tip of the tenth left costal cartilage to the tip of the ninth right cartilage, and the sides by two lines drawn from the end of the eighth left costal cartilage to the ends of the base line. 9

FIG. 1224– Topography of thoracic and abdominal viscera. (See enlarged image)

A space of some clinical importance—the space of Traube—overlies the stomach and may be thus indicated. It is semilunar in outline and lies within the following boundaries: the lower edge of the left lung, the anterior border of the spleen, the left costal margin and the inferior margin of the left lobe of the liver. 10

Duodenum (Fig. 1225).—The superior part is horizontal and extends from the pylorus to the right lateral line; the descending part is situated medial to the right lateral line, from the transpyloric line to a point midway between the transpyloric and transtubercular lines. The horizontal part runs with a slight upward slope from the end of the descending part to the left of the middle line; the ascending part is vertical, and reaches the transpyloric line, where it ends in the duodenojejunal flexure, about 2.5 cm. to the left of the middle line. 11

FIG. 1225– Front of abdomen, showing surface markings for duodenum, pancreas, and kidneys. A A’. Plane through joint between body and xiphoid process of sternum. B B’. Plane midway between A A’ and transpyloric plane. C C’. Plane midway between transpyloric and transtubercular planes. (See enlarged image)

Small Intestine.—The coils of small intestine occupy the front of the abdomen. For the most part the coils of the jejunum are situated on the left side, i.e., in the left lumbar and iliac regions, and in the left half of the umbilical region. The coils of the ileum lie toward the right in the right lumbar and iliac regions, in the right half of the umbilical region, and in the hypogastric region; a portion of the ileum is within the pelvis. The end of the ileum, i.e., the ileocolic junction, is slightly below and medial to the intersection of the right lateral and transtubercular lines. 12

Cecum and Vermiform Process.—The cecum is in the right iliac and hypogastric regions; its position varies with its degree of distension, but the midpoint of a line drawn from the right anterior superior iliac spine to the upper margin of the symphysis pubis will mark approximately the middle of its lower border. 13
The position of the base of the vermiform process is indicated by a point on the lateral line on a level with the anterior superior iliac spine. 14

Ascending Colon.—The ascending colon passes upward through the right lumbar region, lateral to the right lateral line. The right colic flexure is situated in the upper and right angle of intersection of the subcostal and right lateral lines. 15

Transverse Colon.—The transverse colon crosses the abdomen on the confines of the umbilical and epigastric regions, its lower border being on a level slightly above the umbilicus, its upper border just below the greater curvature of the stomach. 16

Descending Colon.—The left colic flexure is situated in the upper left angle of the intersection between the left lateral and transpyloric lines. The descending colon courses down through the left lumbar region, lateral to the left lateral line, as far as the iliac crest (see footnote p. 1181). 17

Iliac Colon.—The line of the iliac colon is from the end of the descending colon to the left lateral line at the level of the anterior superior iliac spine. 18

Liver (Fig. 1223).—The upper limit of the right lobe of the liver, in the middle line, is at the level of the junction between the body of the sternum and the xiphoid process; on the right side the line must be carried upward as far as the fifth costal cartilage in the mammary line, and then downward to reach the seventh rib at the side of the thorax. The upper limit of the left lobe can be defined by continuing this line downward and to the left to the sixth costal cartilage, 5 cm. from the middle line. The lower limit can be indicated by a line drawn 1 cm. below the lower margin of the thorax on the right side as far as the ninth costal cartilage, thence obliquely upward to the eighth left costal cartilage, crossing the middle line just above the transpyloric plane and finally, with a slight left convexity, to the end of the line indicating the upper limit. 19
According to Birmingham the limits of the normal liver may be marked out on the surface of the body in the following manner. Take three points: (a) 1.25 cm. below the right nipple; (b) 1.25 cm. below the tip of the tenth rib; (c) 2.5 cm. below the left nipple. Join (a) and (c) by a line slightly convex upward; (a) and (b) by a line slightly convex lateralward; and (b) and (c) by a line slightly convex downward. 20
The fundus of the gall-bladder approaches the surface behind the anterior end of the ninth right costal cartilage close to the lateral margin of the Rectus abdominis. 21

Pancreas (Fig. 1225).—The pancreas lies in front of the second lumbar vertebra. Its head occupies the curve of the duodenum and is therefore indicated by the same lines as that viscus; its neck corresponds to the pylorus. Its body extends along the transpyloric line, the bulk of it lying above this line to the tail which is in the left hypochondriac region slightly to the left of the lateral line and above the transpyloric. 22

Spleen (Figs. 1217, 1226).—To map out the spleen the tenth rib is taken as representing its long axis; vertically it is situated between the upper border of the ninth and the lower border of the eleventh ribs. The highest point is 4 cm. from the middle line of the back at the level of the tip of the ninth thoracic spinous process; the lowest point is in the midaxillary line at the level of the first lumbar spinous process. 23

Kidneys (Figs. 1225, 1226).—The right kidney usually lies about 1 cm. lower than the left, but for practical purposes similar surface markings are taken for each. 24
On the front of the abdomen the upper pole lies midway between the plane of the lower end of the body of the sternum and the transpyloric plane, 5 cm. from the middle line. The lower pole is situated midway between the transpyloric and intertubercular planes, 7 cm. from the middle line. The hilum is on the transpyloric plane, 5 cm. from the middle line. Round these three points a kidney-shaped figure 4 cm. to 5 cm. broad is drawn, two-thirds of which lies medial to the lateral line. To indicate the position of the kidney from the back, the parallellogram of Morris is used; two vertical lines are drawn, the first 2.5 cm., the second 9.5 cm. from the middle line; the parallelogram is completed by two horizontal lines drawn respectively at the levels of the tips of the spinous process of the eleventh thoracic and the lower border of the spinous process of the third lumbar vertebra. The hilum is 5 cm. from the middle line at the level of the spinous process of the first lumbar vertebra. 25

Ureters.—On the front of the abdomen, the line of the ureter runs from the hilum of the kidney to the pubic tubercle; on the back, from the hilum vertically downward, passing practically through the posterior superior iliac spine (Fig. 1226). 26

FIG. 1226– Back of lumbar region, showing surface markings for kidneys, ureters, and spleen. The lower portions of the lung and pleura are shown on the right side. (See enlarged image)

FIG. 1227– Front of abdomen, showing surface markings for arteries and inguinal canal. (See enlarged image)

Vessels (Fig. 1227).—The inferior epigastric artery can be marked out by a line from a point midway between the anterior superior iliac spine and the pubic symphysis to the umbilicus. This line also indicates the lateral boundary of Hesselbach’s triangle—an area of importance in connection with inguinal hernia; the other boundaries are the lateral edge of Rectus abdominis, and the medial half of the inguinal ligament. The line of the abdominal aorta begins in the middle line about 4 cm. above the transpyloric line and extends to a point 2 cm. below and to the left of the umbilicus—or more accurately to a point 2 cm. to the left of the middle line on a line which passes through the highest points of the iliac crests (A A’, Fig. 1227). The point of termination of the abdominal aorta corresponds to the level of the fourth lumbar vertebra; a line drawn from it to a point midway between the anterior superior iliac spine and the symphysis pubis indicates the common and external iliac arteries. The common iliac is represented by the upper third of this line, the external iliac by the remaining two-thirds. 27
Of the larger branches of the abdominal aorta, the celiac artery is 4 cm., the superior mesenteric 2 cm. above the transpyloric line; the renal arteries are 2 cm. below the same line. The inferior mesenteric artery is 4 cm. above the bifurcation of the abdominal aorta. 28

Nerves.—The thoracic nerves on the anterior abdominal wall are represented by lines continuing those of the bony ribs. The termination of the seventh nerve is at the level of the xiphoid process, the tenth reaches the vicinity of the umbilicus, the twelfth ends about midway between the umbilicus and the upper border of the symphysis pubis. The first lumbar is parallel to the thoracic nerves; its iliohypogastric branch becomes cutaneous above the subcutaneous inguinal ring; its ilioinguinal branch at the ring.

9. Surface Anatomy of the Perineum

Skin.—In the middle line of the posterior part of the perineum and about 4 cm. in front of the tip of the coccyx is the anal orifice. The junction of the mucous membrane of the anal canal with the skin of the perineum is marked by a white line which indicates also the line of contact of the external and internal Sphincters. In the anterior part of the perineum the external genital organs are situated. The skin covering the scrotum is rough and corrugated, but over the penis it is smooth; extending forward from the anus on to the scrotum and penis is a median ridge which indicates the scrotal raphé. In the female are seen the skin reduplications forming the labia majora and minora laterally, the frenulum of the labia behind, and the prepuce of the clitoris in front; still more anteriorly is the mons pubis. 1

Bones.—In the antero-lateral boundaries of the perineum, the whole outline of the pubic arch can be readily traced ending in the ischial tuberosities. Behind in the middle line is the tip of the coccyx. 2

Muscles and Ligaments.—The margin of the Glutæus maximus forms the postero-lateral boundary, and in thin subjects, by pressing deeply, the sacrotuberous ligament can be felt through the muscle. The only other muscles influencing surface form are the Ischiocavernosus covering the crus penis, which lies on the side of the pubic arch, and the Sphincter ani externus, which, in action, closes the anal orifice and causes a puckering of the skin around it. 3

10. Surface Markings of the Perineum

A line drawn transversely across in front of the ischial tuberosities divides the perineum into a posterior or rectal, and an anterior or urogenital, triangle. This line passes through the central point of the perineum, which is situated about 2.5 cm. in front of the center of the anal aperture or, in the male, midway between the anus and the reflection of the skin on to the scrotum. 1

Rectum and Anal Canal.—A finger inserted through the anal orifice is grasped by the Sphincter ani externus, passes into the region of the Sphincter ani internus, and higher up encounters the resistance of the Puborectalis; beyond this it may reach the lowest of the transverse rectal folds. In front, the urethral bulb and membranous part of the urethra are first identified, and then about 4 cm. above the anal orifice the prostate is felt; beyond this the vesiculæ seminales, if enlarged, and the fundus of the bladder, when distended, can be recognized. On either side is the ischiorectal fossa. Behind are the anococcygeal body, the pelvic surfaces of the coccyx and lower end of the sacrum, and the sacrospinous ligaments (Fig. 1228). 2
In the female the posterior wall and fornix of the vagina, and the cervix and body of the uterus can be felt in front, while somewhat laterally the ovaries can just be reached. 3

FIG. 1228– Median sagittal section of male pelvis. (See enlarged image)

Male Urogenital Organs.—The corpora cavernosa penis can be followed backward to the crura which are attached to the sides of the pubic arch. The glans penis, covered by the prepuce, and the external urethral orifice can be examined, and the course of the urethra traced along the under surface of the penis to the bulb which is situated immediately in front of the central point of the perineum. Through the wall of the scrotum on either side the testis can be palpated; it lies toward the back of the scrotum, and along its posterior border the epididymis can be felt; passing upward along the medial side of the epididymis is the spermatic cord, which can be traced upward to the subcutaneous inguinal ring. 4
By means of a sound the general topography of the urethra and bladder can be investigated; with the urethroscope the interior of the urethra can be illuminated and viewed directly; with the cystoscope the interior of the bladder is in a similar manner illuminated for visual examination. In the bladder the main points to which attention is directed are the trigone, the torus uretericus, the plicæ uretericæ, and the openings of the ureters and urethra (see Fig. 1240). 5

Female Urogenital Organs.—In the pudendal cleft (Fig. 1229) between the labia minora are the openings of the vagina and urethra. In the virgin the vaginal opening is partly closed by the hymen—after coitus the remains of the hymen are represented by the carunculæ hymenales. Between the hymen and the frenulum of the labia is the fossa navicularis, while in the groove between the hymen and the labium minus, on either side, the small opening of the greater vestibular (Bartholin’s) gland can be seen. These glands when enlarged can be felt on either side of the posterior part of the vaginal orifice. By inserting a finger into the vagina the following structures can be examined through its wall (Fig. 1230). Behind, from below upward, are the anal canal, the rectum, and the rectouterine excavation. Projecting into the roof of the vagina is the vaginal portion of the cervix uteri with the external uterine orifice; in front of and behind the cervix the anterior and posterior vaginal fornices respectively can be examined. With the finger in the vagina and the other hand on the abdominal wall the whole of the cervix and body of the uterus, the uterine tubes, and the ovaries can be palpated. If a speculum be introduced into the vagina, the walls of the passage, the vaginal portion of the cervix, and the external uterine orifice can all be exposed for visual examination. 6

FIG. 1229– External genital organs of female. The labia minora have been drawn apart. (See enlarged image)

FIG. 1230– Median sagittal section of female pelvis. (See enlarged image)

The external urethral orifice lies in front of the vaginal opening; the angular gap in which it is situated between the two converging labia minora is termed the vestibule. The urethral canal in the female is very dilatable and can be explored with the finger. About 2.5 cm. in front of the external orifice of the urethra are the glans and prepuce of the clitoris, and still farther forward is the mons pubis. 7

11. Surface Anatomy of the Upper Extremity

Skin.—The skin covering the shoulder and arm is smooth and very movable on the underlying structures. In the axilla there are numerous hairs and many sudoriferous and sebaceous glands. Over the medial side and front of the forearm the skin is thin and smooth, and contains few hairs but many sudoriferous glands; over the lateral side and back of the arm and forearm it is thicker, denser, and contains more hairs but fewer sudoriferous glands. In the region of the olecranon it is thick and rough, and is very loosely connected to the underlying tissue so that it falls into transverse wrinkles when the forearm is extended. At the front of the wrist there are three transverse furrows in the skin; they correspond respectively from above downward to the positions of the styloid process of the ulna, the wrist-joint, and the midcarpal joint. 1
The skin of the palm of the hand differs considerably from that of the forearm. At the wrist it suddenly becomes hard and dense and covered with a thick layer of epidermis; on the thenar eminence these characteristics are less marked than elsewhere. In spite of its hardness and density the skin of the palm is exceedingly sensitive and very vascular, but it is destitute of hairs and sebaceous glands. It is tied down by fibrous bands along the lines of flexion of the digits, exhibiting certain furrows of a permanent character. One of these, starting in front of the wrist at the tuberosity of the navicular bone, curves around the thenar eminence and ends on the radial border of the hand a little above the metacarpophalangeal joint of the index finger. A second line begins at the end of the first and extends obliquely across the palm to reach the ulnar border about the middle of the fifth metacarpal bone. A third line begins at the ulnar border about 2.5 cm. distal to the end of the second and extends across the heads of the fifth, fourth, and third metacarpal bones. The proximal segments of the fingers are joined to one another on the volar aspect by folds of skin constituting the “web” of the fingers; these folds extend across about the level of the centers of the proximal phalanges and their free margins are continuous with the transverse furrows at the roots of the fingers. Since the web is confined to the volar aspect the fingers appear shorter when viewed from in front than from behind. 2
Over the fingers and thumb the skin again becomes thinner, especially at the flexures of the joints (where it is crossed by transverse furrows) and over the terminal phalanges; it is disposed on numerous ridges in consequence of the arrangement of the papillæ in it. These ridges form, in different individuals, distinctive and permanent patterns which can be used for purposes of identification. The superficial fascia in the palm of the hand is made up of dense fibro-fatty tissue which binds the skin so firmly to the palmar aponeurosis that very little movement is permitted between the two. 3
On the back of the hand and fingers the subcutaneous tissue is lax, so that the skin is freely movable on the underlying parts. Over the interphalangeal joints the skin is very loose and is thrown into transverse wrinkles when the fingers are extended. 4

Bones.—The clavicle can be felt throughout its entire length. The enlarged sternal extremity projects above the upper margin of the sternum at the side of the jugular notch, and from this the body of the bone can be traced lateralward immediately under the skin. The medial part is convex forward, but the surface is partially obscured by the attachments of Sternocleidomastoideus and Pectoralis major; the lateral third is concave forward and ends at the acromion of the scapula in a slight enlargement. The clavicle is almost horizontal when the arm is lying by the side, although in muscular subjects it may incline a little upward at its acromial end, which is on a plane posterior to the sternal end. 5
The only parts of the scapula that are truly subcutaneous are the spine and acromion, but the coracoid process, the vertebral border, the inferior angle, and to a lesser extent the axillary border can also be readily defined. The acromion and spine are easily recognizable throughout their entire extent, forming with the clavicle the arch of the shoulder. The acromion forms the point of the shoulder; it joins the clavicle at an acute angle—the acromial angle—slightly medial to, and behind the tip of the acromion. The spine can be felt as a distinct ridge, marked on the surface as an oblique depression which becomes less distinct and ends in a slight dimple a little lateral to the spinous processes of the vertebræ. Below this point the vertebral border can be traced downward and lateralward to the inferior angle, which can be identified although covered by Latissimus dorsi. From the inferior angle the axillary border can usually be traced upward through its thick muscular covering, forming with its enveloping muscles the posterior fold of the axilla. The coracoid process is situated about 2 cm. below the junction of the intermediate and lateral thirds of the clavicle; it is covered by the anterior border of Deltoideus, and thus lies a little lateral to the infraclavicular fossa or depression which marks the interval between the Pectoralis major and Deltoideus. 6
The humerus is almost entirely surrounded by muscles, and the only parts which are strictly subcutaneous are small portions of the medial and lateral epicondyles; in addition to these, however, the tubercles and a part of the head of the bone can be felt under the skin and muscles by which they are covered. Of these, the greater tubercle forms the most prominent bony point of the shoulder, extending beyond the acromion; it is best recognized when the arm is lying passive by the side, for if the arm be raised it recedes under the arch of the shoulder. The lesser tubercle, directed forward, is medial to the greater and separated from it by the intertubercular groove, which can be made out by deep pressure. When the arm is abducted the lower part of the head of the humerus can be examined by pressing deeply in the axilla. On either side of the elbow-joint and just above it are the medial and lateral epicondyles. Of these, the former is the more prominent, but the medial supracondylar ridge passing upward from it is much less marked than the lateral, and as a rule is not palpable; occasionally, however, the hook-shaped supracondylar process (page 211) is found on this border. The position of the lateral epicondyle is best seen during semiflexion of the forearm, and is indicated by a depression; from it the strongly marked lateral supracondylar ridge runs upward. 7
The most prominent part of the ulna, the olecranon, can always be identified at the back of the elbow-joint. When the forearm is flexed the upper quadrilateral surface is palpable, but during extension it recedes into the olecranon fossa. During extension the upper border of the olecranon is slightly above the level of the medial epicondyle and nearer to this than to the lateral; when the forearm is fully flexed the olecranon and the epicondyles form the angles of an equilateral triangle. On the back of the olecranon is a smooth triangular subcutaneous surface, and running down the back of the forearm from the apex of this triangle the prominent dorsal border of the ulna can be felt in its whole length: it has a sinuous outline, and is situated in the middle of the back of the limb above; but below, where it is rounded off, it can be traced to the small subcutaneous surface of the styloid process on the medial side of the wrist. The styloid process forms a prominent tubercle continuous above with the dorsal border and ending below in a blunt apex at the level of the wrist-joint; it is most evident when the hand is in a position midway between supination and pronation. When the forearm is pronated another prominence, the head of the ulna, appears behind and above the styloid process. 8
Below the lateral epicondyle of the humerus a portion of the head of the radius is palpable; its position is indicated on the surface by a little dimple, which is best seen when the arm is extended. If the finger be placed in this dimple and the semiflexed forearm be alternately pronated and supinated the head of the radius will be felt distinctly, rotating in the radial notch. The upper half of the body of the bone is obscured by muscles; the lower half, though not subcutaneous, can be readily examined, and if traced downward is found to end in a lozenge-shaped convex surface on the lateral side of the base of the styloid process; this is the only subcutaneous part of the bone, and from its lower end the apex of the styloid process bends medialward toward the wrist. About the middle of the dorsal surface of the lower end of the radius is the dorsal radial tubercle, best perceived when the wrist is slightly flexed; it forms the lateral boundary of the oblique groove for the tendon of Extensor pollicis longus. 9
On the front of the wrist are two subcutaneous eminences, one, on the radial side, the larger and flatter, produced by the tuberosity of the navicular and the ridge on the greater multangular; the other, on the ulnar side, by the pisiform. The tuberosity of the navicular is distal and medial to the styloid process of the radius, and is most clearly visible when the wrist-joint is extended; the ridge on the greater multangular is about 1 cm. distal to it. The pisiform is about 1 cm. distal to the lower end of the ulna and just distal to the level of the styloid process of the radius; it is crossed by the uppermost crease which separates the front of the forearm from the palm of the hand. The rest of the volar surface of the bony carpus is covered by tendons and the transverse carpal ligament, and is entirely concealed, with the exception of the hamulus of the hamate bone, which, however, is difficult to define. On the dorsal surface of the carpus only the triangular bone can be clearly made out. 10
Distal to the carpus the dorsal surfaces of the metacarpal bones, covered by the Extensor tendons, except the fifth, are visible only in very thin hands; the dorsal surface of the fifth is, however, subcutaneous throughout almost its whole length. Slightly lateral to the middle line of the hand is a prominence, frequently well-marked, but occasionally indistinct, formed by the styloid process of the third metacarpal bone; it is situated about 4 cm. distal to the dorsal radial tubercle. The heads of the metacarpal bones can be plainly seen and felt, rounded in contour and standing out in bold relief under the skin when the fist is clenched; the head of the third is the most prominent. In the palm of the hand the metacarpal bones are covered by muscles, tendons, and aponeuroses, so that only their heads can be distinguished. The base of the metacarpal bone of the thumb, however, is prominent dorsally, distal to the styloid process of the radius; the body of the bone is easily palpable, ending at the head in a flattened prominence, in front of which are the sesamoid bones. 11
The enlarged ends of the phalanges can be easily felt. When the digits are bent the proximal phalanges form prominences, which in the joints between the first and second phalanges are slightly hollow, but flattened and square-shaped in those between the second and third. 12

Articulations.—The sternoclavicular joint is subcutaneous, and its position is indicated by the enlarged sternal extremity of the clavicle, lateral to the long cord-like sternal head of Sternocleidomastoideus. If this muscle be relaxed a depression between the end of the clavicle and the sternum can be felt, defining the exact position of the joint. 13
The position of the acromioclavicular joint can generally be ascertained by determining the slightly enlarged acromial end of the clavicle which projects above the level of the acromion; sometimes this enlargement is so considerable as to form a rounded eminence. 14
The shoulder-joint is deeply seated and cannot be palpated. If the forearm be slightly flexed a curved crease or fold with its convexity downward is seen in front of the elbow, extending from one epicondyle to the other; the elbow-joint is slightly distal to the center of the fold. The position of the radiohumeral joint can be ascertained by feeling for a slight groove or depression between the head of the radius and the capitulum of the humerus, at the back of the elbow-joint. 15
The position of the proximal radioulnar joint is marked on the surface at the back of the elbow by the dimple which indicates the position of the head of the radius. The site of the distal radioulnar joint can be defined by feeling for the slight groove at the back of the wrist between the prominent head of the ulna and the lower end of the radius, when the forearm is in a state of almost complete pronation. 16
Of the three transverse skin furrows on the front of the wrist, the middle corresponds fairly accurately with the wrist-joint, while the most distal indicates the position of the midcarpal articulation. 17
The metacarpophalangeal and interphalangeal joints are readily available for surface examination; the former are situated just distal to the prominences of the knuckles, the latter are sufficiently indicated by the furrows on the volar, and the wrinkles on the dorsal surfaces. 18

Muscles (Figs. 1194, 1231, 1232).—The anterior border of the Trapezius presents as a slight ridge running downward and forward from the superior nuchal line of the occipital bone to the junction of the intermediate and lateral thirds of the clavicle. The inferior border of the muscle forms an undulating ridge passing downward and medialward from the root of the spine of the scapula to the spinous process of the twelfth thoracic vertebra. 19
The lateral border of the Latissimus dorsi (Fig. 1215) may be traced, when the muscle is in action, as a rounded edge starting from the iliac crest and slanting obliquely forward and upward to the axilla, where it takes part with the Teres major in forming the posterior axillary fold. 20
The Pectoralis major (Fig. 1219) conceals a considerable part of the thoracic wall in front. Its sternal origin presents a border which bounds, and determines the width of the sternal furrow. The upper margin is generally well-marked medially and forms the medial boundary of a triangular depression, the infraclavicular fossa, which separates the Pectoralis major from the Deltoideus; it gradually becomes less marked as it approaches the tendon of insertion and is closely blended with the Deltoideus. The lower border of Pectoralis major forms the rounded anterior axillary fold. Occasionally a gap is visible between the clavicular and sternal parts of the muscle. 21
When the arm is raised the lowest slip of origin of Pectoralis minor produces a fulness just below the anterior axillary fold and serves to break the sharp outline of the lower border of Pectoralis major. 22
The origin of the Serratus anterior (Figs. 1215, 1219) causes a very characteristic surface marking. When the arm is abducted the lower five or six serrations form a zigzag line with a general convexity forward; when the arm is by the side the highest visible serration is that attached to the fifth rib. 23
The Deltoideus with the prominence of the upper end of the humerus produces the rounded contour of the shoulder; it is rounded and fuller in front than behind, where it presents a somewhat flattened form. Above, its anterior border presents a slightly curved eminence which forms the lateral boundary of the infraclavicular fossa; below, it is closely united with the Pectoralis major. Its posterior border is thin, flattened, and scarcely marked above, but is thicker and more prominent below. The insertion of Deltoideus is marked by a depression on the lateral side of the middle of the arm. 24

FIG. 1231– Front of right upper extremity. (See enlarged image)

Of the scapular muscles the only one which influences surface form is the Teres major; it assists the Latissimus dorsi in forming the thick, rounded, posterior axillary fold. 25
When the arm is raised the Coracobrachialis reveals itself as a narrow elevation emerging from under cover of the anterior axillary fold and running medial to the body of the humerus. 26

FIG. 1232– Back of right upper extremity. (See enlarged image)

On the front and medial aspects of the arm is the prominence of the Biceps brachii, bounded on either side by an intermuscular depression. It determines the contour of the front of the arm and extends from the anterior axillary fold to the bend of the elbow; its upper tendons are concealed by the Pectoralis major and Deltoideus, and its lower tendon sinks into the anticubital fossa. When the muscle is fully contracted it presents a globular form, and the lacertus fibrosus attached to its tendon of insertion becomes prominent as a sharp ridge running downward and medialward. 27
On either side of the Biceps brachii at the lower part of the arm the Brachialis is discernible. Laterally it forms a narrow eminence extending some distance up the arm; medially it exhibits only a little fulness above the elbow. 28
On the back of the arm the long head of the Triceps brachii may be seen as a longitudinal eminence, emerging from under cover of Deltoideus and gradually passing into the flattened plane of the tendon of the muscle at the lower part of the back of the arm. When the muscle is in action the medial and lateral heads become prominent. 29
On the front of the elbow are two muscular elevations, one on either side, separate above but converging below so as to form the medial and lateral boundaries of the anticubital fossa. The medial elevation consists of the Pronator teres and the Flexors, and forms a fusiform mass, pointed above at the medial epicondyle and gradually tapering off below. The Pronator teres is the most lateral of the group, while the Flexor carpi radialis, lying to its medial side, is the most prominent and may be traced downward to its tendon, which is situated nearer to the radial than to the ulnar border of the front of the wrist and medial to the radial artery. The Palmaris longus presents no surface marking above, but below, its tendon stands out when the muscle is in action as a sharp, tense cord in front of the middle of the wrist. The Flexor digitorum sublimis does not directly influence surface form; the position of its four tendons on the front of the lower part of the forearm is indicated by an elongated depression between the tendons of Palmaris longus and Flexor carpi ulnaris. The Flexor carpi ulnaris determines the contour of the medial border of the forearm, and is separated from the Extensor group of muscles by the ulnar furrow produced by the subcutaneous dorsal border of the ulna; its tendon is evident along the ulnar border of the lower part of the forearm, and is most marked when the hand is flexed and adducted. 30
The elevation forming the lateral side of the anticubital fossa consists of the Brachioradialis, the Extensors and the Supinator; it occupies the lateral and a considerable part of the dorsal surface of the forearm in the region of the elbow, and forms a fusiform mass which is altogether on a higher level than that produced by the medial elevation. Its apex is between the Triceps brachii and Brachialis some distance above the elbow-joint; it acquires its greatest breadth opposite the lateral epicondyle, and below this shades off into a flattened surface. About the middle of the forearm it divides into two diverging longitudinal eminences. The lateral eminence consists of the Brachioradialis and the Extensores carpi radiales longus and brevis, and descends from the lateral supracondylar ridge in the direction of the styloid process of the radius. The medial eminence comprises the Extensor digitorum communis, Extensor digiti quinti proprius, and the Extensor carpi ulnaris; it begins at the lateral epicondyle of the humerus as a tapering mass which is separated above from the Anconæus by a well-marked furrow, and below from the Pronator teres and Flexor group by the ulnar furrow. The medial border of the Brachioradialis starts as a rounded elevation above the lateral epicondyle; lower down the muscle forms a prominent mass on the radial side of the upper part of the forearm; below it tapers to its tendon, which may be traced to the styloid process of the radius. The Anconæus presents as a triangular slightly elevated area, immediately lateral to the subcutaneous surface of the olecranon and differentiated from the Extensor group by an oblique depression; the upper angle of the triangle is at the dimple over the lateral epicondyle. 31
At the lower part of the back of the forearm in the interval between the two diverging eminences is an oblique elongated swelling; full above but flattened and partially subdivided below; it is caused by the Abductor pollicis longus and the Extensor pollicis brevis. It crosses the dorsal and lateral surfaces of the radius to the radial side of the wrist-joint, whence it is continued on to the dorsal surface of the thumb as a ridge best marked when the thumb is extended. 32
The tendons of most of the Extensor muscles can be seen and felt on the back of the wrist. Laterally is the oblique ridge produced by the Extensor pollicis longus. The Extensor carpi radialis longus is scarcely palpable, but the Extensor carpi radialis brevis can be identified as a vertical ridge emerging from under the ulnar border of the tendon of the Extensor pollicis longus when the wrist is extended. Medial to this the Extensor tendons of the fingers can be felt, the Extensor digiti quinti proprius being separated from the tendons of the Extensor digitorum communis by a slight furrow. 33
The muscles of the hand are principally concerned, as regards surface form, in producing the thenar and hypothenar eminences, and cannot be individually distinguished; the thenar eminence, on the radial side, is larger and rounder than the hypothenar, which is a long narrow elevation along the ulnar side of the palm. When the Palmaris brevis is in action it produces a wrinkling of the skin over the hypothenar eminence and a dimple on the ulnar border. On the back of the hand the Interossei dorsales give rise to elongated swellings between the metacarpal bones; the first forms a prominent fusiform bulging when the thumb is adducted, the others are not so marked. 34

Arteries.—Above the middle of the clavicle the pulsation of the subclavian artery can be detected by pressing downward, backward, and medialward against the first rib. The pulsation of the axillary artery as it crosses the second rib can be felt below the middle of the clavicle just medial to the coracoid process; along the lateral wall of the axilla the course of the artery can be easily followed close to the medial border of Coracobrachialis. The brachial artery can be recognized in practically the whole of its extent, along the medial margin of the Biceps; in the upper two-thirds of the arm it lies medial to the humerus, but in the lower third is more directly on the front of the bone. Over the lower end of the radius, between the styloid process and Flexor carpi radialis, a portion of the radial artery is superficial and is used clinically for observations on the pulse. 35

Veins.—The superficial veins of the upper extremity are easily rendered visible by compressing the proximal trunks; their arrangement is described on pages 660 to 662. 36

Nerves.—The uppermost trunks of the brachial plexus are palpable for a short distance above the clavicle as they emerge from under the lateral border of Sternocleidomastoideus; the larger nerves derived from the plexus can be rolled under the finger against the lateral axillary wall but cannot be identified. The ulnar nerve can be detected in the groove behind the medial epicondyle of the humerus. 37

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Skin.—The skin of the thigh, especially in the hollow of the groin and on the medial side, is thin, smooth and elastic, and contains few hairs except on the neighborhood of the pubis. Laterally it is thicker and the hairs are more numerous. The junction of the skin of the thigh with that on the front of the abdomen is marked by a well-defined furrow which indicates the site of the inguinal ligament; the furrow presents a general convexity downward, but its medial half, which is the better marked, is nearly straight.

The skin over the buttock is fairly thick and is characterized by its low sensibility and slight vascularity; as a rule it is destitute of conspicuous hairs except toward the post-anal furrow, where in some males they are abundantly developed. An almost transverse fold—the gluteal fold—crosses the lower part of the buttock; it practically bisects the lower margin of the Glutæus maximus and is most evident during extension of the hip-joint.

The skin over the front of the knee is covered by thickened epidermis; it is loose and thrown into transverse wrinkles when the leg is extended. The skin of the leg is thin, especially on the medial side, and is covered with numerous large hairs. On the dorsum of the foot the skin is thin, loosely connected to subjacent parts, and contains few hairs, on the plantar surface, and especially over the heel, the epidermis is of great thickness, and here, as in the palm of the hand, there are neither hairs nor sebaceous glands.

Bones.—The hip bones are largely covered with muscles, so that only at a few points do they approach the surface.

In front the anterior superior iliac spine is easily recognized, and in thin subjects stands out as a prominence at the lateral end of the fold of the groin; in fat subjects its position is indicated by an oblique depression, at the bottom of which the bony process can be felt.

Proceeding upward and backward from this process the sinuously curved iliac crest can be traced to the posterior superior iliac spine, the site of which is indicated by a slight depression; on the outer lip of the crest, about 5 cm. behind the anterior superior spine, is the prominent iliac tubercle.

In thin subjects the pubic tubercle is very apparent, but in the obese it is obscured by the pubic fat; it can, however, be detected by following up the tendon of origin of Adductor longus.

Another part of the bony pelvis which is accessible to touch is the ischial tuberosity, situated beneath the Glutæus maximus, and, when the hip is flexed, easily felt, as it is then uncovered by muscle.

The femur is enveloped by muscles, so that in fairly muscular subjects the only accessible parts are the lateral surface of the greater trochanter and the lower expanded end of the bone.

The site of the greater trochanter is generally indicated by a depression, owing to the thickness of the Glutæi medius and minimus which project above it; when, however, the thigh is flexed, and especially if it be crossed over the opposite one, the trochanter produces a blunt eminence on the surface.

The lateral condyle is more easily felt than the medial; both epicondyles can be readily identified, and at the upper part of the medial condyle the sharp adductor tubercle can be recognized without difficulty. When the knee is flexed a portion of the patellar surface is uncovered and is palpable.

The anterior surface of the patella is subcutaneous. When the knee is extended the medial border of the bone is a little more prominent than the lateral, and if the Quadriceps femoris be relaxed the bone can be moved from side to side. When the joint is flexed the patella recedes into the hollow between the condyles of the femur and the upper end of the tibia, and becomes firmly applied to the femur.

A considerable portion of the tibia is subcutaneous. At the upper end the condyles can be felt just below the knee; the medial condyle is broad and smooth, and merges into the subcutaneous surface of the body below; the lateral is narrower and more prominent, and on it, about midway between the apex of the patella and the head of the fibula, is the tubercle for the attachment of the iliotibial band.

In front of the upper end of the bone, between the condyles, is an oval eminence, the tuberosity, which is continuous below with the anterior crest of the bone. This crest can be identified in the upper two-thirds of its extent as a flexuous ridge, but in the lower third it disappears and the bone is concealed by the tendons of the muscles on the front of the leg.

Medial to the anterior crest is the broad surface, slightly encroached on by muscles in front and behind. The medial malleolus forms a broad prominence, situated at a higher level and somewhat farther forward than the lateral malleolus; it overhangs the medial border of the arch of the foot; its anterior border is nearly straight, its posterior presents a sharp edge which forms the medial margin of the groove for the tendon of Tibialis posterior.

The only subcutaneous parts of the fibula are the head, the lower part of the body, and the lateral malleolus. The head lies behind and lateral to the lateral condyle of the tibia, and presents as a small prominent pyramidal eminence slightly above the level of the tibial tuberosity; its position can be readily located by following downward the tendon of Biceps femoris.

The lateral malleolus is a narrow elongated prominence, from which the lower third or half of the lateral surface of the body of the bone can be traced upward.

On the dorsum of the tarsus the individual bones cannot be distinguished, with the exception of the head of the talus, which forms a rounded projection in front of the ankle-joint when the foot is forcibly extended. The whole dorsal surface of the foot has a smooth convex outline, the summit of which is the ridge formed by the head of the talus, the navicular, the second cuneiform, and the second metatarsal bone; from this it inclines gradually lateralward, and rapidly medialward.

On the medial side of the foot the medial process of the tuberosity of the calcaneus and the ridge separating the posterior from the medial surface of the bone are distinguishable; in front of this, and below the medial malleolus, is the sustentaculum tali. The tuberosity of the navicular is palpable about 2.5 to 3 cm. in front of the medial malleolus.

Farther forward, the ridge formed by the base of the first metatarsal bone can be obscurely felt, and from this the body of the bone can be traced to the expanded head; beneath the base of the first phalanx is the medial sesamoid bone.

On the lateral side of the foot the most posterior bony point is the lateral process of the tuberosity of the calcaneus, with the ridge separating the posterior from the lateral surface of the bone. In front of this the greater part of the lateral surface of the calcaneus is subcutaneous; on it, below and in front of the lateral malleolus, the trochlear process, when present, can be felt. Farther forward the base of the fifth metatarsal bone is prominent, and from it the body and expanded head can be traced.

As in the case of the metacarpals, the dorsal surfaces of the metatarsal bones are easily defined, although their heads do not form prominences; the plantar surfaces are obscured by muscles. The phalanges in their whole extent are readily palpable.

Articulations.—The hip-joint is deeply seated and cannot be palpated.

The interval between the tibia and femur can always be easily felt; if the knee-joint be extended this interval is on a higher level than the apex of the patella, but if the joint be slightly flexed it is directly behind the apex. When the knee is semiflexed, the medial borders of the patella and of the medial condyle of the femur, and the upper border of the medial condyle of the tibia, bound a triangular depressed area which indicates the position of the joint.

The ankle-joint can be felt on either side of the Extensor tendons, and during extension of the joint the superior articular surface of the talus presents below the anterior border of the lower end of the tibia.

FIG. 1238– Front and medial aspect of right thigh. (See enlarged image)

Muscles.—Of the muscles of the thigh, those of the anterior femoral region (Fig. 1238) contribute largely to surface form.

The Tensor fasciæ latæ produces a broad elevation immediately below the anterior part of the iliac crest and behind the anterior superior iliac spine; from its lower border a groove caused by the iliotibial band extends downward to the lateral side of the knee-joint.

The upper portion of Sartorius constitutes the lateral boundary of the femoral triangle, and, when the muscle is in action, forms a prominent oblique ridge which is continued below into a flattened plane and then gradually merges into a general fulness on the medial side of the knee-joint. When the Sartorius is not in action, a depression exists between the Quadriceps femoris and the Adductors, and extends obliquely downward and medialward from the apex of the femoral triangle to the side of the knee.

In the angle formed by the divergence of Sartorius and Tensor fasciæ lataæ, just below the anterior superior iliac spine, the Rectus femoris appears, and in a muscular subject its borders can be clearly defined when the muscle is in action.

The Vastus lateralis forms a long flattened plane traversed by the groove of the iliotibial band. The Vastus medialis gives rise to a considerable prominence on the medial side of the lower half of the thigh; this prominence increases toward the knee and ends somewhat abruptly with a full curved outline.

The Vastus intermedius is completely hidden. The Adductores cannot be differentiated from one another, with the exception of the upper tendon of Adductor longus and the lower tendon of Adductor magnus.

When the Adductor longus is in action its upper tendon stands out as a prominent ridge running obliquely downward and lateralward from the neighborhood of the public tubercle, and forming the medial border of the femoral triangle.

The lower tendon of Adductor magnus can be distinctly felt as a short ridge extending downward between the Sartorius and Vastus medialis to the adductor tubercle. The adductores fill in the triangular space at the upper part of the thigh, between the femur and the pelvis, and to them is due the contour of the medial border of the thigh, the Gracilis contributing largely to the smoothness of the outline.

FIG. 1239– Back of left lower extremity.

The Glutæus maximus (Fig. 1239) forms the full rounded outline of the buttock; it is more prominent behind, compressed in front, and ends at its tendinous insertion in a depression immediately behind the greater trochanter; its lower border crosses the gluteal fold obliquely downward and lateralward.

The upper is part of Glutæus medius visible, but its lower part with Glutæus minimus and the external rotators are completely hidden. From beneath the lower margin of Glutæus maximus the hamstrings appear; at first they are narrow and not well-defined, but as they descend they become more prominent and eventually divide into two well-marked ridges formed by their tendons; these constitute the upper boundaries of the popliteal fossa.

The tendon of Biceps femoris is a thick cord running to the head of the fibula; the tendons of the Semimembranosus and Semitendinosus as they run medialward to the tibia are separated by a slight furrow; the Semitendinosus is the more medial, and can be felt in certain positions of the limb as a sharp cord, while the Semimembranosus is thick and rounded. The Gracilis is situated a little in front of them.

The Tibialis anterior (Fig. 1240) presents a fusiform enlargement at the lateral side of the tibia and projects beyond the anterior crest of the bone; its tendon can be traced on the front of the tibia and ankle-joint and thence along the medial side of the foot to the base of the first metatarsal bone.

The fleshy fibers of Peronæus longus are strongly marked at the upper part of the lateral side of the leg; it is separated by furrows from Extensor digitorum longus in front and Soleus behind. Below, the fleshy fibers end abruptly in a tendon which overlaps the more flattened elevation of Peronæus brevis; below the lateral malleolus the tendon of Peronæus brevis is the more marked.

On the dorsum of the foot (Fig. 1241) the tendons emerging from beneath the transverse and cruciate crural ligaments spread out and can be distinguished as follows: the most medial and largest is Tibialis anterior, the next is Extensor hallucis proprius, then Extensor digitorum longus dividing into four tendons, to the second, third, fourth, and fifth toes, and lastly Peronæus tertius.

The Extensor digitorum brevis produces a rounded outline on the dorsum of the foot and a fulness in front of the lateral malleolus. The Interossei dorsales bulge between the metatarsal bones.

FIG. 1240– Lateral aspect of right leg.

At the back of the knee is the popliteal fossa, bounded above by the tendons of the hamstrings and below by the Gastrocnemius. Below this fossa is the prominent fleshy mass of the calf of the leg produced by Gastrocnemius and Soleus (Fig. 1239).

When these muscles are in action the borders of Gastrocnemius form two well-defined curved lines which converge to the tendocalcaneus; the medial border is the more prominent. At the same time the edges of Soleus can be seen forming, on either side of Gastrocnemius, curved eminences, of which the lateral is the longer.

The fleshy mass of the calf ends somewhat abruptly in the tendocalcaneus, which tapers in the upper three-fourths of its extent but widens out slightly below. Behind the medial border of the lower part of the tibia (Fig. 1242) a well-defined ridge is produced by the tendon of Tibialis posterior during contraction of the muscle.

On the sole of the foot the Abductor digiti quinti forms a narrow rounded elevation on the lateral side, and the Abductor hallucis a lesser elevation on the medial side. The Flexor digitorum brevis, bound down by the plantar aponeurosis, is not very apparent; it produces a flattened form, and the thickened skin underlying it is thrown into numerous wrinkles.

FIG. 1241– The mucous sheaths of the tendons around the ankle. Lateral aspect.

Arteries.—The femoral artery as it crosses the brim of the pelvis is readily felt; in its course down the thigh its pulsation becomes gradually more difficult of recognition. When the knee is flexed the pulsation of the popliteal artery can easily be detected in the popliteal fossa.

FIG. 1242– The mucous sheaths of the tendons around the ankle. Medial aspect.

On the lower part of the front of the tibia the anterior tibial artery becomes superficial and can be traced over the ankle into the dorsalis pedis; the latter can be followed to the proximal end of the first intermetatarsal space. The pulsation of the posterior tibial artery becomes evident near the lower end of the back of the tibia, and is easily detected behind the medial malleolus.

Veins.—By compressing the proximal trunks, the venous arch on the dorsum of the foot, together with the great and small saphenous veins leading from it (see page 669), are rendered visible.

Nerves.—The only nerve of the lower extremity which can be located by palpation is the common peroneal as it winds around the lateral side of the neck of the fibula.

14. Surface Markings of the Lower Extremity

Bony Landmarks.—The anterior superior iliac spine is at the level of the sacral promontory—the posterior at the level of the spinous process of the second sacral vertebra. A horizontal line through the highest points of the iliac crests passes also through the spinous process of the fourth lumbar vertebra, while, as already pointed out (page 1315), the transtubercular plane through the tubercles on the iliac crests cuts the body of the fifth lumbar vertebra. The upper margin of the greater sciatic notch is opposite the spinous process of the third sacral vertebra, and slightly below this level is the posterior inferior iliac spine.

The surface markings of the posterior inferior iliac spine and the ischial spine are both situated in a line which joins the posterior superior iliac spine to the outer part of the ischial tuberosity; the posterior inferior spine is 5 cm. and the ischial spine 10 cm. below the posterior superior spine; the ischial spine is opposite the first piece of the coccyx.

With the body in the erect posture the line joining the public tubercle to the top of the greater trochanter is practically horizontal; the middle of this line overlies the acetabulum and the head of the femur.

FIG. 1243– Nélaton’s line and Bryant’s triangle. (See enlarged image)

FIG. 1244– Left gluteal region, showing surface markings for arteries and sciatic nerve.

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FIG. 1245– Front of right thigh, showing surface markings for bones, femoral artery and femoral nerve.

FIG. 1246– Lateral aspect of right leg, showing surface markings for bones, anterior tibial and dorsalis pedis arteries, and deep peroneal nerve.

FIG. 1247– Back of left lower extremity, showing surface markings for bones, vessels, and nerves. (See enlarged image)

A line used for clinical purposes is that of Nélaton (Fig. 1243), which is drawn from the anterior superior iliac spine to the most prominent part of the ischial tuberosity; it crosses the center of the acetabulum and the upper border of the greater trochanter. Another surface marking of clinical importance is Bryant’s triangle, which is mapped out thus: a line from the anterior superior iliac spine to the top of the greater trochanter forms the base of the triangle; its sides are formed respectively by a horizontal line from the anterior superior iliac spine and a vertical line from the top of the greater trochanter.

Articulations.—The posterior superior iliac spine overlies the center of the sacroiliac articulations.

The hip-joint may be indicated, as described above, by the center of a horizontal line from the pubic tubercle to the top of the greater trochanter; or more generally, it is below and slightly lateral to the middle of the inguinal ligament.

The knee-joint is superficial and requires no surface marking.

The level of the ankle-joint is that of a transverse line about 1 cm. above the level of the tip of the medial malleolus. If the foot be forcibly extended, the head of the talus appears as a rounded prominence on the medial side of the dorsum; just in front of this prominence and behind the tuberosity of the navicular is the talonavicular joint.

The calcaneocuboid joint is situated midway between the lateral malleolus and the prominent base of the fifth metatarsal bone; the line indicating it is parallel to that of the talonavicular joint. The line of the fifth tarsometatarsal joint is very oblique; it starts from the projection of the base of the fifth metatarsal bone, and if continued would pass through the head of the first metatarsal.

The lines of the fourth and third tarsometatarsal joints are less oblique. The first tarsometatarsal joint corresponds to a groove which can be felt by making firm pressure on the medial border of the foot 2.5 cm. in front of the tuberosity of the navicular bone; the position of the second tarsometatarsal joint is 1.25 cm. behind this. The metatarsophalangeal joints are about 2.5 cm. behind the webs of the corresponding toes.

Muscles.—None of the muscles require any special surface lines to indicate them, but there are three intermuscular spaces which occasionally require definition, viz., the femoral triangle, the adductor canal, and the popliteal fossa.

The femoral triangle is bounded above by the inguinal ligament, laterally by the medial border of Sartorius, and medially by the medial border of Adductor longus. In the triangle is the fossa ovalis, through which the great saphenous vein dips to join the femoral; the center of this fossa is about 4 cm. below and lateral to the pubic tubercle, its vertical diameter measures about 4 cm. and its transverse about 1.5 cm. The femoral ring is about 1.25 cm. lateral to the pubic tubercle.

The adductor canal occupies the medial part of the middle third of the thigh; it begins at the apex of the femoral triangle and lies deep to the vertical part of Sartorius.

The popliteal fossa is bounded: above and medially by the tendons of Semimembranosus and Semitendinosus; above and laterally by the tendon of Biceps femoris; below and medially by the medial head of Gastrocnemius; below and laterally by the lateral head of Gastrocnemius and the Plantaris.

Mucous Sheaths.—The positions of the mucous sheaths around the tendons about the ankle-joints are sufficiently indicated in Figs. 1241, 1242 (see also page 489).

Arteries.—The points of emergence of the three main arteries on the buttock, viz., the superior and inferior gluteals and the internal pudendal, may be indicated in the following manner (Fig. 1244). With the femur slightly flexed and rotated inward, a line is drawn from the posterior superior iliac spine to the posterior superior angle of the greater trochanter; the point of emergence of the superior gluteal artery from the upper part of the greater sciatic foramen corresponds to the junction of the upper and middle thirds of this line.

A second line is drawn from the posterior superior iliac spine to the outer part of the ischial tuberosity; the junction of its lower with its middle third marks the point of emergence of the inferior gluteal and internal pudendal arteries from the lower part of the greater sciatic foramen. The course of the femoral artery (Fig. 1245) is represented by the upper two-thirds of a line from a point midway between the anterior superior iliac spine and the symphysis pubis to the adductor tubercle, with the thigh abducted and rotated outward; the profunda femoris arises from it about 1 to 5 cm. below the inguinal ligament.

The course of the upper part of the popliteal artery (Fig. 1247) is indicated by a line from the lateral margin of Semimembranosus at the junction of the middle and lower thirds of the thigh, obliquely downward to the middle of the popliteal fossa; from this point it runs vertically downward for about 2.5 cm. or to the level of a line through the lower part of the tibial tuberosity.

The line indicating the anterior tibial artery (Fig. 1246) is drawn from the medial side of the head of the fibula to a point midway between the malleoli; the artery begins about 3 cm. below the head of the fibula. The dorsalis pedis artery is represented on the dorsum of the foot by a line from the center of the interval between the malleoli to the proximal end of the first intermetatarsal space.

The course of the posterior tibial artery (Fig. 1247) can be shown by a line from the end of the popliteal artery, i. e., 2.5 cm. below the center of the popliteal fossa, to midway between the tip of the medial malleolus and the center of the convexity of the heel; its main branch, the peroneal artery, begins about 7 or 8 cm. below the level of the knee-joint and follows the line of the fibula to the back of the lateral malleolus.

The medial and lateral plantar arteries begin from the end of the posterior tibial; the medial extends to the middle of the plantar surface of the ball of the great toe, the lateral to within a finger’s breadth of the tuberosity of the fifth metatarsal bone; from this latter point the plantar arch crosses the foot transversely to the proximal end of the first intermetatarsal space.

Veins.—The line of the great saphenous vein is from the front of the medial malleolus to the center of the fossa ovalis; the small saphenous vein runs from the back of the lateral malleolus to the center of the popliteal fossa.

Nerves.—The course of the sciatic nerve (Fig. 1247) can be indicated by a line from a point midway between the outer border of the ischial tuberosity and the posterior superior angle of the greater trochanter to the upper angle of the popliteal fossa. The continuation of this line vertically through the center of the popliteal fossa represents the position of the tibial nerve, while the common peroneal nerve follows the line of the tendon of Biceps femoris.

The lines for the deep peroneal nerve and the continuation of the tibial nerve correspond respectively to those for the anterior and posterior tibial arteries.