ORIGIN OF THE CORPUS LUTEUM 141 



in diameter, the measurement ranging from 6 to 8 mm. in some 

 which were distorted by crowding. 2 The surface presented no 

 'stigma' or other sign of impending rupture. On section, they 

 were found to possess the usual three layers, and the membrana 

 granulosa was present and intact, showing no sign of degenera- 

 tion. The wall of that part of the follicle lying deepest in the 

 ovary presents a slightly wavy contour toward the cavity. 



The cells of the granulosa (fig. 4, a) form a layer about six to 

 nine cells deep, or about 0.13 to 0.17 mm. thick. Those cells 

 nearest the membrana propria form an irregular columnar layer, 

 but the upper cells show less semblance of order in their arrange- 

 ment. The cells are round or polyhedral, from 8 x 8/* to 10 x 16^ 

 in diameter (in celloidin sections), with round nuclei 5n or 6/x 

 in diameter. The cytoplasm appears homogeneous after the 

 usual fixing reagents, except for a few vacuoles due to the 

 presence of lipoid substances, as will be explained later. Often 

 the cells possess short processes which meet those of the neigh- 

 boring cells so as to make the tissue resemble a syncytium. 



The theca interna is about 0.09 to 0.10 mm. thick, or a little 

 more than half as thick as the granulosa. Its most striking 

 characteristic is the presence of three to five layers of large 

 'epithelioid' cells, usually from 10 x 17/x to 12 x 17m in diameter, 

 but occasionally reaching larger sizes, up to perhaps 16 x 24/x 

 (fig. 4, b). On section, they are oval, spindle-shaped, or almost 

 rectangular, with their long axes in the circumference of the 

 follicle, so that they usually lie at right angles to the columnar 

 layer of the membrana granulosa. Between the larger cells, and 

 especially along the inner border of the layer formed by them, 

 are others of small size (though still somewhat larger than the 

 granulosa cells), which are similar in appearance to the large 

 theca cells. In material fixed in Bouin's fluid the theca cells 



2 In a previous publication ('15) I fell more or less into the same error of 

 method which I am now imputing to others, and attempted to determine the 

 size of the 'ripe' follicle without knowing the state of the enclosed ovum. The 

 larger follicles there mentioned, however, agree histologically with the accu- 

 rately known specimens described in these pages, and it is therefore likely that 

 my previous conclusions were correct, namely, that the normal mature follicle 

 may attain a diameter of 10 mm. 



