It has become generally accepted that the erythrocytes of the blood can be mobilized rather speedily so as to increase their number in the circulating medium of the body in response to changes of activity or unusual circumstances. The spleen seems to act as a reservoir for the red blood cells—a fact suspected in the middle of the last century but only lately put on the firm basis of experimental proof, notably through researches by Barcroft and his collaborators. After hemorrhage or exercise the spleen experiences a diminution of volume sufficient at times to supply an amount of blood equivalent to one fourth of the total blood volume. When poisoning with carbon monoxide decreases the oxygen-carrying power of the blood the spleen tends to contract, thereby discharging into the general circulation an extra supply of red blood corpuscles which have been held there.
Apparently the long disregarded spleen performs a