INTERNAL SECRETION OF OVARY 271 



of the testicle, which increase before or at the time of heat, 

 mitosis seems to be rare in the epithehal and epithehoid cells 

 of the ovary. 



It is very probable that in man and in many other species 

 the endocrine cells of the ovary become transformed, when 

 they are not undergoing degeneration, into common connective 

 tissue cells or into fibrous connective tissue. In these species 

 there is, from a certain age onwards, a periodic new growth 

 of endocrine cells (corpus luteum periodicum or menstrua- 

 tionis); also, these new endocrine cells persist only for a 

 certain time. 



The new growth of the endocrine cells is especially pro- 

 nounced when ovulation is followed by implantation of a 

 fertilized ovum, i.e., when gravidity takes place (corpus luteum 

 graviditatis). 



The endocrine cells of the corpus luteum graviditatis do 

 not remain in functional activity for the whole duration of 

 gravidity, and the organ finally undergoes sclerotization. 

 Now, in the second half of gravidity other endocrine cells 

 replace the degenerating corpus luteum; these cells originate 

 from the theca interna, and possibly also from the granulosa 

 of the follicles, which at that time undergo atresia in an 

 increased number. 



After gravidity is over new ova ripen and new endocrine 

 cells are produced; a new menstruation or a new heat begins. 



The cyclical uterine changes and the cyclical increase in 

 sexual activity as observable in menstruation and heat, 

 evidently depend upon an activation or a functional increase 

 of the endocrine cells in the ovary. 



From what we have seen above it seems clear that the 

 endocrine function of the ovary is intimately connected 

 with processes taking place in the follicle. Possibly these 

 processes depend upon the ripening of the ovum, though it is 

 not necessary that the ovum should attain maturity. Moreover, 

 it is not even necessary that the ovum should remain alive. 

 There seems to be a far-reaching analogy between the endocrine 

 mechanism of the ovary and that of the testicle in the mammal. 

 In both sexes the post-embryonic transformation of inactive 

 cells of mesodermic or mesenchymatic origin may depend upon 

 impulses coming from the generative tissue without full 

 maturation or without even the further presence of ripening 



