The literature dealing with the influence of endocrine organs on hair growth is not extensive, and the results reported are by no means concordant. In the rat there seems to be a specific influence of the thyroid gland, the administration of which accelerates hair growth in some normal animals, but not all, whereas underfed animals respond more uniformly [Chang, 1926; Chang & Feng, 1929]. Chang & Feng [1929] also noted that thyroidectomy slows the rate at which new hair grows, and found no difference in response between the sexes. They measured the time elapsing before growth on a shaved patch appeared to be complete. Butcher [1940] found that thyroxin and various irritants such as xylene or capsicum decreased the time elapsing before the first appearance of new hair in underfed albino rats, whereas well-fed animals were not much affected. Freud [1934] found that normal, thyroidectomized, epiphysectomized and castrated male rats