EFFECT OF DRY HEAT ON THE BLOOD COUNT IN ANIMALS : III. STUDIES ON LYMPHOID ACTIVITY.

Animals subjected to dry heat for a short period show a sharp fall in the total white blood count, both the polymorphonuclear leucocytes and the lymphocytes taking part in the fall. Following this there is a slow recovery on the part of the polymorphonuclear leucocytes, which generally require several weeks to regain their normal number. The lymphocytes rise rapidly after the initial fall and continue to rise for 2 or 3 weeks. This increase often amounts to a gain of over 200 to 300 per cent above the normal count for the animal. The observations were made on mice, rats, and guinea pigs. The circulating lymphocytes during the more active stage of stimulation after heating show numerous examples of amitotic division.