A method of estimating the total volume of blood contained in the living body

The determination during life of the total volume of blood contained in the living body is usually effected by Haldane’s method. This consists in first estimating the percentage hæmoglobin content of the blood and then determining the total hæmoglobin content of the circulating fluid, the latter being effected by administering a known volume of carbon monoxide and observing the extent to which the hæmoglobin of the red cells is in combination with this gas. Copeman and Sherrington determined the volume of the blood in the living body by injecting a measured volume of 0⋅75-per-cent. solution of sodium chloride (sp. gr. 1⋅0046) and observing the resulting fall in specific gravity of the blood. Recently, while making an investigation upon hæmoglobinæmia, we found it necessary to make estimations of the total amount of blood in the living body. This we carried out by: (1) making a hæmocrit estimation of the relative proportions, by volume, of red cells and plasma; (2) injecting a known quantity of dissolved hæmoglobin into the blood stream and determining the degree of the resulting hæmoglobinæmia, from which the amount of plasma present can be calculated. The method employed thus consists of two procedures, namely the estimation: (1) of the percentage (by volume) of plasma contained in the blood (A ); and (2) of the total volume of plasma contained in the body (B). The total volume of the blood is B/A × 100.