THE CORPUS LUTEUM 725 



connective tissue. Both views have received a considerable 

 number of supporters, but largely owing to the work of Sobotta 



(20) the balance is in favour of Bischoff's view. Van der Stricht 



(21) has put forward yet another theory, that the lutein cells 

 were derived not only from the cells of the membrana granulosa, 

 but also in small part from the cells of the theca interna. 

 On the whole, then, it appears that the lutein cells are 

 derived from the cells of the membrana granulosa, although 

 in some cases perhaps some of them may also be derived from 

 the theca interna. Moreover, although certain investigators 

 (e.g. Sobotta and Van der Stricht) have described the very 

 occasional appearance of mitotic figures in the lutein cells of the 

 growing corpus luteum, there is no doubt that by far the greater 

 number of these cells are simply the transformed and hyper- 

 trophied cells of the membrana granulosa. 



All investigators agree that the connective tissue network is 

 derived from the theca folliculi, but differ in describing the parts 

 taken by its constituent layers. It is stated that the network is 

 derived from the theca interna alone or from this and also from 

 the theca externa. In the Marsupial, Dasyurus, one cannot dis- 

 tinguish between these two layers of the theca. The part 

 played by each layer is not yet decided or may perhaps vary in 

 different species. 



The blood vessels of the corpus luteum appear to take their 

 origin from the vessels of the theca interna and have walls com- 

 posed of a single layer of flattened endothelial cells. They form 

 a network of cavities and resemble the "sinusoids " in the liver 

 and kidney of an Amphibian. Definite blood vessels with the 

 structure of venules or arterioles are not found in the corpus 

 luteum. 



The duration of this body is not known accurately ; it takes 

 but a few days to form and is generally stated to reach its 

 maximum development about the middle of pregnancy, and after 

 that period to decrease gradually, lasting about three months in 

 the rabbit, and also in Dasyurus. During the later stages of its 

 degeneration it loses its characteristic yellow colour and be- 

 comes fibrous and white, whence it is known as the corpus 

 albicans. It finally undergoes fatty degeneration and is ab- 

 sorbed by the aid of leucocytes, while according to some 

 observers a number of its cells become transformed into 

 interstitial cells. 



