A definite increase in the percentage of reticulocytes occurs after exercise in animals previously kept to a sedentary life. Concomitant changes in the hemoglobin percentage, plasma-cell ratio, and red count offer evidence in addition to that already reported by the author of the occurrence of an increase in blood destruction under such circumstances.
Replacement by transfusion of blood destroyed during exercise prevents the reticulated cell reaction. Animals rendered plethoric and then exercised show no increase in reticulated cells while the plethora persists.
The fact is emphasized that exercise must be an important factor in the maintenance of an efficient hematopoietic tissue.