BLOOD DESTRUCTION DURING EXERCISE : IV. THE DEVELOPMENT OF EQUILIBRIUM BETWEEN BLOOD DESTRUCTION AND REGENERATION AFTER A PERIOD OF TRAINING.

Animals recently caged do not show as large a decrease in cell volume after exercise as those which have been confined several months. When a dog kept for a long time under sedentary conditions is exercised continuously for several weeks, a decrease in cell volume occurs in the 1st or 2nd week of exercise, but usually by the end of the 3rd week the loss has been made up. Apparently by this time the hematopoietic tissues have adapted themselves to the increased demands made upon them by the hastened rate of destruction. There is, furthermore, some anatomical evidence that such is the case.