GKAAFIAN FOLLICLES. 277 



hire follicles project just beneath the surface and form little 

 rounded, translucent elevations ; the smallest follicles are near 

 the surface, and, as they enlarge, at first become deeper, as is 

 seen in Fig. 25, becoming superficial only as they approach 

 the period of fullest distention. 



Taking one of the largest follicles as an example, two 

 fibrous layers can be distinguished ; an outer layer, of ordi- 

 nary connective tissue, and an inner layer, the tunica propria, 

 formed of the same kind of tissue, with the difference that, 

 as the follicle enlarges, the inner layer becomes vascular. 1 



O ' / 



The vascular tunica propria is lined by cells of epithelium, 

 forming the so-called membrana granulosa. At a certain 

 point in this membrane, is a mass of cells, called the discus 

 or cumulus proligerus, in which the ovum is embedded. The 

 situation of the discus proligerus and the ovum has been a 

 subject of discussion ; some describe it in the most superficial 

 portion, and others, in the deepest part of the follicle. "Wal- 

 deyer states that he has observed it in both situations ; a and 

 it is probable that its position is not invariable. 



The liquid of the Graafian follicle is alkaline, slightly 

 yellowish, not viscid, and contains a small quantity of albu- 

 minoid matter coagulable by heat, alcohol, and acids. 8 This 

 liquid is supposed to be secreted by the cells lining the inner 

 membrane of the follicle. 



1 Some anatomists describe the two fibrous layers of the Graafian follicle as 

 a single membrane ; and some, who recognize the two layers, state that the outer 

 layer alone is vascular. We have adopted the description of Waldeyer, as given 

 above. 



a WALDEYER, in STRICKER, Manual of Human and Comparative Histology, 

 The New Sydenham Society, London, 1872, vol. ii., p. 174. 



As early as 1847, Pouchet stated that, in numerous observations on the sow, 

 the ovum was ordinarily found near the deepest portion of the Graafian follicle. 

 (POUCHET, Theorie positive de Vovulation spontanee, Paris, 1847, p. 48.) Among 

 the more recent writers, we find that Schrb'n states that the ovum is almost al- 

 ways found at the deepest portion of the follicle. (Beitrag zur Kentniss der 

 Anatomic und Physiologic des Eierstocks der Sdugethiere. Zeitschrift fur wissen- 

 schaftliche Zoologie, Leipzig, 1863, Bd. xii., S. 419.) 



8 ROBIN, Lecons sur les humeurs, Paris, 1867, p. 335. 



