246 INTERNAL SECRETIONS 



speak, for follicular development is very great, there is in an 

 ovarian fragment an almost endless supply available for 

 follicular development or "hypertrophy," unless indeed the 

 fragment is extremely small, as in our last experiment, 

 related above. The case of a testicular fragment seems to be 

 a wholly different one; what takes place in a testicular 

 fragment is only development up to a normal volume corre- 

 sponding to the given fragment of a testicle, since, after 

 completion of spermatogenesis in all the tubules of a fragment, 

 there seems to be no anatomical substratum for further 

 growth. In other words, every cubic millimetre of testicle 

 has a constant maximal potential mass, which is attained 

 when spermatogenesis is completed. On the contrary, a cubic 

 millimetre of ovary has no constant or limited potential mass, 

 the latter depending upon the relative number of ova which 

 enter upon follicular development. It would appear, therefore, 

 that the dynamics of testicular and ovarian growth provide 

 an explanation for the differences as observed in these respects 

 between an ovarian and a testicular fragment. 



The second question is of a more difficult order. There is 

 normally in the female greater variation in the condition of 

 the sex characters, and no doubt exists that this variation is 

 connected with follicular development in the ovary. The 

 relatively larger number of ova entering in an ovarian frag- 

 ment upon follicular development may be considered as 

 participating in a process of reparation or regeneration. 

 There may be some general factors in the female organism 

 regulating the number of follicles in the ovarian tissue, like 

 the factor regulating in the male organism the speed of 

 testicular growth (Lipschutz, 1923 and 1924 a; Lipschiitz and 

 Voss, 1924 c). We have no knowledge of the special localiza- 

 tion of such hypothetical factors. 



6. The Internal Secretion of the Corpus Luteum.^ 



We have seen that genetically the interstitial cells of the 

 ovary belong mostly to the follicular apparatus, and that these 

 cells are, so to speak, discharged from the atretic follicles into 

 the ovarian stroma. Further, we saw it was very probable 

 that these cells represent an endocrine organ, which can hyper- 



^ The new papers of Marshall (1923) and of Corner (1923) and the new 

 edition of Marshall's book (1922) may be referred to here. 



