252 SPECIAL HISTOLOGY. 



brane is the external layer of the original fibrous coat of the 

 follicle ; and as regards the yellow plicated cortical layer, this 

 is referable for the most part to the in- 

 ^JJ^^' ternal layer of the fibrous membrane of 



the original follicle, which even before 

 the expulsion of the ovum, becomes 

 loosened in texture, and afterwards 

 rapidly expanded to the thickness of 

 -J — Jf" and more. The remains of the 

 epithelium, or membrana granulosa, which 

 were not expelled with the ovum from 

 the follicle, also seem to contribute to 

 this thickening, though in a subordinate 

 degree, and by no means in the same 

 proportion as the layer in question; the 

 increased thickness of which is accom- 

 panied by the development of a vast number of smaller and larger 

 cells, which are, in part, transformed into immature connective 

 tissue and vessels, in part remain in the condition of cells, 

 characterised by their size, which reaches as much as 0-01 — 0'2'", 

 their well-marked, vesicular nuclei with nucleoli, and a greater 

 or less number of yellow oil-drops in the interior. The corpus 

 luteum, thus constituted, retains its original size for some time, 

 up to the second or third month of pregnancy; because, whilst 

 the contents (whether these are a blood-clot, or a reddish 

 gelatinous substance with a small cavity in the interior) 

 gradually diminish and lose their colour, the yellow cortical 

 layer continues to increase in thickness, and, at the same time, 

 its tissue to become more organized and more compact; this 

 change taking place by the transformation, on the one side, of 

 the internal substance into fibrous tissue, and on the other by 

 the more intimate fusion of the yellow cortex with it, and the 

 more abundant development of immature connective tissue in 

 the former. In the fourth and fifth months the atrophy of the 

 corpus luteum commences, and is slowly continued to the end 



Fig. 266. Two corpora lutea, of the natural size, in a transverse section. 1, quite 

 recent, eight days after conception; 2, at the fifth month of pregnancy: a, t, albu- 

 ginea ; b, stroma ovarii; c, thickened and plicated fibrous membrane of the follicle 

 (inner layer) ; d, blood-clot within it ; e, discoloured blood-clot ; /, fibrous coat 

 bounding the corpus luteum. 



