HY F. P. SANDES. 373 



spaces are diliereut from other spaces, walled in by cells arranged 

 in an irregular way, due to the liquefaction of the cell cytoplasm 

 after chromatolysis of the nuclei. Definite " corps vesiculeux," 

 with cells radially arranged round them, as first described by 

 Call and Exner in the rabbit — the "Epithelvacuolen" of Flemming 

 — are not seen in Dasyurus, although in the larger primordial 

 follicles and in the young Graafian follicles there are found spaces 

 between irregularly arranged cells, showing in their interior an 

 ill-defined system of trabecuke. These are probably the repre- 

 sentatives of the so-called " corps vesiculeux" of Call and Exner 

 in Dasyurus. >Similar structures are found in atresic follicles. 



The characters of the theca folliculi will be described more fully 

 later on, during the consideration of the ripe follicle. To the 

 whole structure, as above described, consisting of ovum, mem- 

 brana granulosa, and membranes with the theca folliculi, may be 

 applied the term "primordial follicle." 



The Graafian Follicle — its Formation and Ripening. 



The development of the primordial follicle has been described 

 in the preceding section. The next important event in its 

 history is the formation of cavities in the membrana granulosa. 

 This is brought about by liquefaction of the cell contents, follow- 

 ing upon a chromatolysis of its nucleus, a process which can be 

 observed to take place in several places at once, but progresses 

 more rapidly in some places than in others. By the ultimate 

 coalescence of these cavities the ovum is left in the centre of a 

 vesicular structure, lined by cells of the membrana granulosa and 

 connected to it by bands of cells, called " retinacula" (see fig. 4). 

 This structure is called the "Graafian follicle." Its cavity con- 

 tains fluid, formed probably by cell liquefaction and by secretion 

 from them, and by the infiltration of lymph into the cavity. This 

 formation of fluid goes on — evidently against pressure, other 

 spaces appear in the membrana granulosa, the follicle increases 

 greatly in size and becomes ripe. 



