120 Embryonic Development of Ovary and Testis of Mammals 



These fat grannies are very characteristic of the interstitial cells. 

 In this stage certain of these cells which have become isolated from 

 the general mass are found to have enlarged greatly and to have be- 

 come stuffed full of large fat spherules which are very readily dissolved 

 by xylol. Each of these cells contains a large excentric nucleus with 



a centrosphere and centrosome (Plate 

 VII, Fig. 28). Most of the interstitial 

 cells are crowded together by mutual pres- 

 sure and are hence prevented from attain- 

 ing the full size of the one figured, which 

 lay free in the connective tissue. 



8 Months Old; 1st Pregnancy; 1^ 

 Days Pregnant. — The corpora lutea ap- 

 pear to be in the height of their develop- 

 ment. The lutein cells composing them 

 are rounded and suffer very little mutual 

 pressure, being separated by fair intervals 

 in many cases. Between them is a loose 

 mass of fibrous connective tissue. The 

 interstitial cells on the other hand, lie in 

 dense masses between the corpora lutea. 

 They are arranged in parallel strands in 

 the manner already noted. Certain 

 interstitial cells that become separated from the general mass are 

 found to be rounded and of almost the same size as the lutein cells 

 of the corpora lutea. 



One is struck by the great resemblance of the interstitial and lutein 

 cells (Plate VII, Figs. 29 and 30), a resemblance that practically amounts 

 to identity aside from the matter of size, which difference can, in large 

 part, be attributed to the factor of external pressure. The description 

 of the interstitial cells of the 6-months' virgin practically applies to the 

 interstitial cells of this pregnant rabbit and to the lutein cells of the 

 corpora lutea as well. 



Ovaries of Older Pregnant Rahhits. — The ovaries of a number of ani- 

 mals in various stages of pregnancy were examined. In the older of 

 these animals the lutein and interstitial cells are apparently indistin- 

 guishable in the deeper-lying regions where the cells are the oldest. 

 In the most central zones they are found to be undergoing a process of 

 hyaline degeneration, the cell limits becoming indistinct, the cyto- 

 plasm ragged, and the nucleus very faint. Finally the innermost 

 regions are found to contain the shrivelled remains of these cells. 



Fig. 5. Transverse section of 

 ovary of a six-months old virgin 

 rabbit. /'., follicle ; d. /., degenerate 

 follicle ; y. c, germiriative epithe- 

 lium; i. »!., masses of interstitial 

 cells ; I. s., Ijmpli spaces ; m., me- 

 sonephros remains. X 24. 



