A modification of GowerÕs tube (or apparatus) to measure hemoglobin; it is largely of historical interest. It uses two tubes with sample blood measured against a reference tube filled with a ÒnormalÓ patientÕs blood mixed with 10% HCl solution. When the sample blood tube is diluted to the exact same tint as the reference tube, a reading is obtained that will give the % of a normal hemoglobin amount contained in the sample.