Experiments were carried out on 18 adult [male] over a period of 3 mos. The authors observed the average daily activity to be essentially the same as before removal of the glands. The feeding of thyroid gland substance caused a slight decrease, while castration and spaying greatly decreases the spontaneous activity with comparatively slight decrease in basal metabolism. They conclude that the basal metabolic level does not show any close correspondence with the amount of spontaneous activity manifested.