574 HEEBEET M. EVANS 



erable size but they invariably degenerate by death of both the ova and 

 .granulosa, whereupon the next adjacent enveloping cells of the ovarian 

 stroma the cells of the so-called theca interna undergo a peculiar hyper- 

 trophy and activity, surviving for a very considerable time after the follicle 

 about which they were first formed has entirely disappeared. So extensive 

 are these peculiar processes which attend prepubertal follicular degenera- 

 tion or atresia, that the gland comes to possess throughout its substance 

 many cell clumps and strands formed by these cells of the theca interna. 

 Indeed, even in the postpubertal life of many mammals, these cells may 

 be similarly so abundant and so diffuse as to constitute at times the main 

 mass of tissue of the ovary. These are the ovarian interstitial cells. Their 

 origin from the theca interna was first clearly made out by the French his- 

 tologist Limon (a). It has been claimed that they alone are responsible 

 for the gradual unfolding of the secondary sex characters during early 

 development, a thesis which has been especially defended in great detail 

 by Lipschutz. Their function would be then presumably enormously 

 increased during that time of "flowering out" of the sex characters known 

 as the puberty period itself. Quantitative studies which would show a 

 great increase of such cells at exactly this time are unfortunately not at 

 hand, and there is even evidence, indeed, that with the occurrence of the 

 first ovulation, function of the interstitial substance rapidly recedes in 

 importance. Furthermore, we do not possess proof that the secondary sex 

 characters are all delayed in expression until the formation of the intersti- 

 tial cells by follicular atresia can be demonstrated as occurring or as hav- 

 ing taken place. 



But an identification of the ovarian interstitial cells with the develop- 

 ment of characters distinguishing the female sex has been supported by 

 other studies than those on embryology and growth. Steinach and Moore 

 have transplanted ovaries into young castrated males and believe that one 

 may thereby effect changes in the sex characters of the host involving the 

 surrender of masculine and the acquirement of feminine traits which 

 further express themselves, for instance, in the modification of such a 

 general phenomenon as the rate of growth. The ovary normally retards 

 the growth of the female and exercises the same effect when transplanted 

 to castrated males. Steinach and Athias indeed have demonstrated that 

 in such experiments there may ultimately appear a hypertrophy of the 

 mammary glands of the male host and a true secretion of milk so that he 

 is able to adopt offspring. The ovaries in such transplants do not for a 

 long time depart greatly from the normal, as found by Sand and by Mar- 

 shall and Jolly, and as I have been able to confirm in experiments with 

 Long ; for a time they continue to ovulate and form corpora lutea regularly 

 but Steinach and Lipschutz describe them as having eventually lost all 

 trace of true luteal structures and as coming to possess merely a great 

 number of obliterated follicles which are peculiar hybrid growths in 



