Preliminary experiments on more than 200 human subjects had demonstrated an "activity level" of 8000-9000 leucocytes per cu. mm., and a "basal leucocyte level" during immobility of (usually) 5000-6000 per cu. mm. The present experiments showed that in recumbent resting subjects heavy protein or carbohydrate meals cause no leucocytosis. A slight and transient rise occurred in 5 leucocyte counts after gastric distension or change in temp. through rapid drinking of large quantities of fluid, especially hot. Animal experiments indicated that the reactions are independent of nutriment, and due solely to reflex vascular disturbances.