250 MANUAL OF HISTOLOGY. 



reaches its full development in a few weeks after the raptur- 

 ing of the follicle, or when impregnation has occurred after the 

 lapse of two or three months. It consists of a central portion, 

 at first red, becoming gray, and a peripheral portion, yellow in 

 color, thrown into folds. These folds are made up of the in- 

 ternal membrane and cells. The central portion in a fresh 

 corpus luteum consists of a very vascular tissue, in which are 

 seen numerous large cells, containing a red coloring substance 

 and hsematoidin crystals. A retrograde metamorphosis occurs 

 in the yellow body, supposed to be due to a want of nutrition 

 caused by a wasting of the arteries, and there only remains a 

 white cicatrix, the corpus albicans. The time required for 

 the disappearance of a corpus luteum when impregnation has 

 taken place a true corpus luteum is several months, lasting 

 to the end of gestation ; but for the disappearance of a false 

 corpus luteum, or when impregnation has not occurred, it only 

 requires a few weeks. It is, however, to be remembered, that 

 every Graafian follicle with its contents does not reach full de- 

 velopment ; most of them experience fatty or colloid metamor- 

 phosis. 



The ovaries have their origin from the Wolffian bodies. A 

 thickening of the epithelial covering is early observed upon 

 the side of these bodies ; at the same time and place a cellular 

 projection growing from the connective tissue of the organ is 

 noticed. From this increase of epithelium the Graafian folli- 

 cles and ova are developed, later the ovarial epithelium ; from 

 the connective tissue is built up the vascular system of the ovary. 



The Graafian follicles are developed from collections of cells, 

 irregular in shape, or, as they are named, ova chains, consisting 

 of small-sized peripheral cells, which later form the membrana 

 granulosa, and the primordial ova ; these last are recognized 

 by their large size, granular or reticulated protoplasm and 

 central position. The ova chains are sometimes enclosed in a 

 homogeneous membrana propria, forming a tubular structure, 

 as in the cat ; this membrane, however, is not found in all ani- 

 mals. These chains are developed by an ingrowth of the epi- 

 thelial cells covering the surface of the ovary. 



The parovarium, or remains of the Wolffian body, situated 

 in the broad ligament, is made up of twelve to fifteen tubules, 

 which possess a membrana propria, lined by a single layer of 

 ciliated epithelium, and contain a transparent substance. 



