THE REPRODUCTIVE ORGANS 81 



been stated that there is a considerable difference in the 

 activities of extracts from different animals. It is said that 

 extracts of ovary raise the metabolism in castrated animals, 

 and have a stimulating action on uterine contraction. It is 

 doubtful whether these effects are specific. 



A considerable amount of work has been carried out upon 

 the structure and functions of the corpus luteum. This body 

 in its fully formed state consists of columns of large cells 

 (luteal cells) containing a yellowish pigment. The columns 

 are separated by intervening trabeculse, composed of fibrous 

 tissue containing numerous bloodvessels. These trabeculae 

 converge inwards from the surrounding ovarian stroma to a 

 central strand or plug of connective tissue, in which there are 

 no luteal cells, occupying the axis of the nodule (see Fig. 13). 

 The columns of cells are not unlike those of the cortex of the 

 adrenal (see Figs. 13 and 13a). The fully developed corpus 

 luteum is a highly vascular structure. 



The fullest and most complete account both of the develop- 

 ment and of the histology of the fully formed corpus luteum is 

 given by Sobotta. In the mouse the epithelial cells are large 

 and polygonal in shape, measuring 20 p or more in diameter. 

 The cells contain fat, which is mostly disposed excentrically, 

 but it may almost fill the entire cell. The peripheral cells are for 

 the most part free from fat, while those in the centre contain 

 the largest amount. Generally speaking, the older a corpus 

 luteum is the more fat does it contain. The nucleus is rounded. 

 The connective tissue is in the form of spindle-shaped anasto- 

 mosing cells. They surround groups of four to five epithelial 

 cells by anastomoses of their processes. Their nuclei closely 

 resemble those of the capillary walls. The connective tissue 

 of the central plug consists of stellate elements. In some 

 animals the fully formed luteal cells are rounded or spindle- 

 shaped, and may show signs of degeneration. 



The mode of formation of the corpus luteum is still under 

 discussion. Former investigators were not able to agree as 

 to whether the body is a connective-tissue structure, or whether 

 the luteal cells are formed by the hypertrophy of the epithelial 

 cells of the undischarged Graafian follicle. The former theory 

 is that of v. Baer, the latter that of Bischoff. The investiga- 

 tions of Sobotta upon the mouse and the guinea-pig confirm 

 Bischoff 's view, but there have been several investigators 



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