It may be added that the operation of ligature of the vas deferens which was performed some 25 years ago, before prostatectomy became established, in order to cause atrophy of enlarged prostate, was not noticed to be followed by rejuvenescence. Mr. C. Mansell-Moullin, who published[119] a series of 14 such cases, has kindly informed me that his patients did not show any evidence of such a change. Romeis has also raised this objection to Steinach’s results which it has been thought might be explained by suggestion (Freudenberg)--a view hardly tenable in the light of the remarkable results described in animal experiments. The internal secretion of the ovary has never been isolated, and the evidence of its existence rests on the results of removal. Castration in men and in women does not bring on the phenomena of old age, though this operation is followed by well-marked changes as regards the secondary sex-characters, and, according to Voronoff, eunuchs are short-lived. It may also be pointed out that the obesity so common after castration is not a feature of “the lean and slippered pantaloon.” Further, after the menopause the ovaries undergo fibrotic atrophy, and it appears from Professor Turnbull’s observations (_vide_ p. 114) that the interstitial cells are very scanty or absent; further observations are necessary as to the presence of interstitial cells in senescent ovaries, but presuming that they are scanty it would follow, on the hypothesis that the interstitial cells exert an influence in preventing the onset of old age, that women should become old much sooner than men in whom the interstitial cells are apparently much more in evidence. It cannot of course be admitted that such a difference in the sex incidence of old age exists. The improved health and rejuvenation after _x_-ray treatment for metrorrhagia and uterine fibromyomas at the climacteric or post-climacteric age have been regarded by Steinach and Bordier as due to hypertrophy of the ovarian interstitial cells following induced atrophy of the ova, but to accept this there must be definite evidence that the interstitial cells are increased in number. Harrower’s[120] dictum that the absence of a hormone provided by the interstitial cells is responsible for premature senility does not appear to be borne out by our present knowledge, but a great deal of further work must be done before a final decision is justified. Testicular and ovarian extracts, often in combination with those of the thyroid and pituitary, which are known to have a definite physiological action, have been extensively used as a panacea. But is there any undeniable evidence that the extracts of testis and ovary so far employed have any effect apart from that of suggestion? According to Frank[121] the available ovarian preparations are defatted and thus deficient in the potent lipoid extracts; and very serious doubts as to the activity of testicular extracts have been expressed by Professor Cushny.