No. 2.] THE OVARIAN STROM A OF MAMMALS. 



8 9 



Ovaries of the white rat and of the cat from both pregnant and 

 non-pregnant animals have been examined, but without finding 

 anything similar to the sphere in the dog and the rabbit, 

 although the cells of the stroma show a very similar structure 

 in other respects. It would appear, then, from the facts cited 

 above that the presence of the sphere has some relation to the 

 period of pregnancy, though of what nature it is impossible to 

 state. Furthermore, a 

 sphere of this kind is 

 found only in certain 

 mammals, though 

 others show changes in 

 the structure of the 

 stroma similar to those 

 observed in the dog 

 and rabbit. 



Below is given a 

 short description of 

 the finer structure of 

 these cells as found in 

 the rabbit, but both 

 description and figures 

 apply equally well to 

 the cells of the dog as 

 far as sphere and cen- FIG. i. 



trosome are concerned. 



Fig. i 1 shows a group of these cells as they lie in the ovary. 

 The stroma is made up almost entirely of these cells, the 

 spindle-shaped cells of the ordinary stroma being almost wholly 

 absent. Figs. 2 and 3 show single cells. As is readily seen, 

 the nucleus does not usually occupy the center of the cell, but 

 is often pushed considerably toward one side. When the section 

 happens to be in a favorable plane, as in four of the cells in 

 Fig. i, there is seen on one side of the nucleus -- usually on 

 the side toward the greater mass of cytoplasm - - a large, con- 



1 A jJj Leitz oil immersion lens was used in the study of these cells, and the 

 figures are all drawn with an Abbe camera. They do not show the relations with 

 anything like the clearness of the actual preparation, which was fixed in acetic 

 sublimate and stained with Heidenhain's iron haematoxylin followed by orange G. 



