Many of the changes observed by Prof. Asian in the procaine-treated old people indicate that this substance acts upon the endocrine glands. Hair growth, as already mentioned, is stimulated; some testicular function, often almost dormant, is revived; small amounts of estrogen (the female sex hormone) are found circulating in old women again (the return of pigmentation to the labia minora is only another sign of estrogenic stimulation); the adrenal glands become more active. The involution of female genitals usually is halted after several years’ treatment, and in a few cases has even been reversed.