52 THE CORPUS LUTEUM. 



layer of soft yellowish matter appears in them.* When the follicle bursts, 

 this yellowish deposit increases. It does not, however, usually form mam- 

 millary growths projecting into the cavity of the follicle, and never pro- 

 trudes from the orifice, as is the case in other mammalia. It maintains 

 the character of a uniform, or nearly uniform layer, which is thrown into 

 wrinkles in consequence of the contraction of the external tunic of the 

 follicle. After the orifice of the follicle has closed, the growth of the 

 yellow substance continues during the first half of pregnancy, till the 

 cavity is reduced to a comparatively small size, or is obliterated ; in the 

 latter case, merely a white stelliform cicatrix remaining in the centre of the 

 yellow body. 



In some mammalia as well as in the human subject, an effusion of blood 

 generally takes place into the cavity of the Graafian follicle at the time of 

 its rupture, but in the latter it is more constant and in greater quantity 

 than in the former. The effused blood, however, has in no case any share 

 in forming the yellow body. It gradually loses its colouring matter and 

 acquires the character of a mass of fibrin. The serum of the blood some- 

 times remains included within a cavity in the centre of the coagulum, 

 and then the decolorized fibrin forms a membraniform sac, lining the 

 corpus luteum. At other times the serum of the blood is removed, and 

 the fibrin constitutes a solid stelliform mass. 



There has been much difference of opinion as to the origin of the 

 growth which forms the yellow body. But most of the modern writers of 

 high authority who appear to have examined the corpora lutea in the 

 earliest stage of their growth, with the aid of the microscope, Valentin, R. 

 Wagner, Bischoff, Raciborski, and Zwicky, corroborate the statements of 

 Haller and Von Baer, that the growth arises from the inner surface of the 

 follicle ; and shew that it is, in fact, the result of an increased develop- 

 ment of the cells forming the membrana granulosa which lines the in- 

 ternal tunic of the Graafian follicle. 



The mode of formation of the corpus luteum in the cow and sow has 

 been made the subject of a minute microscopic investigation by Zwicky, 

 the accuracy of which, in all important points, has been verified by the writer. 



The Graafian follicle, according to Zwicky, has really but one tunic or 

 theca, which, although separable into two layers, is throughout composed 

 of the same elements; namely, granular nucleated cells, in part round 

 and varying in size, and in part becoming elongated into fibres (fibre-cells). 

 (Fig. 4, A.) The conversion of the cells into fibres is further advanced 

 in proportion as they are nearer to the outer surface of the theca, where 

 they can no longer be distinguished from the fibres forming the stroma of 

 the ovary. Floating in the fluid contents of the follicle, are granular 

 nucleated cells, round, ovate, or fusiform, and similar to those forming 

 the innermost stratum of the theca. 



* Negrier, Ritchie. 



