TUE OVA AND OVARY IN MAN AND OTHEK MAMMALIA. 211 



Only those connective tissue corpuscles which lie in actual 

 contact with the yelk of the ovum in the follicle develop 

 into corpuscles of the membrana granulosa ; while those in 

 the wall outside the membrana granulosa remain as con- 

 nective tissue corpuscles, and follow the usual developmental 

 process into ordinary fibrous tissue, of which the main part 

 of the follicular wall at last consists. We shall afterwards 

 see that in some of the oldest Graafian follicles in the adult 

 ovary, in man and other mammals, which are about to burst 

 to liberate the contained ovum, a great part of the wall of 

 the follicle outside the membrana granulosa becomes again 

 converted into large connective tissue corpuscles. 



When first formed, the membrana granulosa consists of a 

 single layer of minute corpuscles arranged in the form of a 

 capsule round the ovum (fig. 12, r). As the young ovum 

 enlarges, which it rapidly does after the formation of the 

 membrana granulosa, it distends its follicle, and the corpuscles 

 of the membrana granulosa increase greatly in number. In 

 this membrane, when first formed, the corpuscles lie in close 

 contact with each other, and when looked down upon from 

 above they present a polygonal form from mutual com- 

 pression (fig. 14, r). By the constant multiplication by 

 division of its corpuscles, the membrana granulosa at last 

 comes to consist of several layers. As a further stage in 

 development, certain of the corpuscles, generally those in the 

 middle parts of the membrana granulosa, break down, 

 and become dissolved in a fluid which afterwards forms 

 the liquor folliculi. By the breaking down and solu- 

 tion of these corpuscles, a cavity, the follicular space 

 occupied by fluid, is formed. In section, this space appears 

 semilunar in form. After the formation of this space the 

 ovum is not entirely separated from the membrana granulosa, 

 but remains connected with the wall of the follicle by a heap 

 of corpuscles which surrounds it. In good specimens a layer 

 of corpuscles remains in contact with the zona pellucida 

 round the ovum for a long time after the formation of the 

 follicular space. When first formed, the corpuscles of the 

 membrana gi-anulosa in the human foetal ovary of seven and 

 a half months measure about -j-^^^th inch. 



For the complete demonstration of the development of the 

 corpuscles of the membrana granulosa, the ovary of an adult 

 rabbit is admirably suited. In a section of such an ovary, 

 we first direct our attention to the structure of the stroma of 

 the organ, and we find it consist entirly of very minute 

 attenuated fusiform corpuscles. At first sight these appear 

 as simple fibres, but each fibre is an elongated nucleus, 



