INTERSTITIAL CELLS OF MAMMALIAN OVARY 67 



Graafian follicles are exceedingly irregular, atypical, and ulti- 

 mately undergo atresia. The follicular growth processes and 

 conditions are different in the immature ovary, itself undergoing 

 rapid growth. In the growth of the ovary the stroma obviously 

 plays an important part, and in nowise is to be thought of as 

 playing a passive, purely supportive role. 



In the above exceedingly brief outline of the morphogenesis 

 of the ovary I have presented the conclusions reached in a study 

 of the later development of the ovary. In general there has 

 been full confirmation of the monographic investigation by v. 

 Winiwarter and Saimont. In certain respects, however, the em- 

 phasis, point of view, or interpretation has been different. These 

 riiatters of divergent interpretation have been discussed in the 

 previously published article on the morphogenesis. 



The growth of the ovary is a continuous process, and the rec- 

 ognition of periods is rather artificial; however, it is convenient 

 to distinguish (a) period of early (1st) proliferation; (b) the 

 period of later (2d) proliferation; (c) postpartum period — up to 

 the establishment of definite cortex of resting follicles; charac- 

 terized by development of medullary follicles; (d) the presexual 

 period; growth of the pluri-ovular large medullary follicles; 

 (e) the period of profound degeneration; (f) sexual maturity; 

 (g) senescence. 



The interstitial cells first make their appearance during the 

 second period, being largely associated with the medullary cords, 

 and hence central. Small groups of them, however, occur con- 

 stantly in the stromal septa between the egg cords in the primi- 

 tive cortex (figs. 1 and 2). From this period on, the interstitial 

 cells are present in the ovary of the cat into extreme old age. 

 How early they are present in the fetal ovary I cannot say. 

 The youngest ovary in which they were identified was from a 

 95-mm. fetus. Inasmuch as the series of younger ovaries were 

 not prepared by a method^ that rendered their identification 



* Two methods were used with advantage: (a) Flemming's fluid (Hermann's 

 or Benda's) fixation, the chloroform paraffin imbedding method, the sections being 

 mounted unstained and without coverglass under a thin fihu of chloroform balsam. 

 In toto staining with carmine might, I believe, have been advantageously em- 



