CORPUS LUTEUM IN OVARY OF THE CHICKEN 15 



have a double origin, from granulosa and theca interna, while 

 others such as B(>nthin and Hegar, claim that they all come 

 from the theca interna. This point is perfectly clear in birds 

 due to the ease with which one can distinguish these peculiar 

 cells in the internal theca of undischarged follicles and follow 

 them to the thickened mass in the center of the discharged 

 follicles, and see them migrating out into the cavity of the atretic 

 follicles. 



The formation of a corpus luteum in atretic as well as dis- 

 charged follicles makes it possible to identify ovarian tissue in 

 ovaries too abnormal to have ovulated any eggs. Most of the 

 literature of the mammalian ovary considers the involution of 

 the atretic follicle as something distinct from that of the dis- 

 charged follicle. The mass forming in the atretic follicle is 

 called the corpus atreticum or fibrosum in contradistinction to 

 the corpus luteum. However, Hegar says that it is hard to tell 

 one from the other. They are practically identical in the hen, 



VII. SUMMARY 



We are now in a position to sum up the points proving the 

 homology of the corpus luteum in the hen and in the cow. There 

 has been much discussion about the origin of the corpus luteum 

 in mammals. In the hen there is no question but that the 

 origin is simply from the theca interna. 



The course of development in the hen corpus luteum is an 

 abbreviation or fore-shortening of that in the cow. It corre- 

 sponds directly to the late involution stages of the cow corpus 

 luteum. They both contain a yellow fatty substance, as shown 

 by the Sudan III, absolute alcohol and xylol reactions. There 

 develops in both a yellow amorphous pigment in the cells con- 

 taining the fatty substance. This pigment is similar chemically 

 in that it will not stain with basic or acid stains; also in that 

 it will not dissolve in any of the usual solvents, acid alkali 

 or oil. 



In the hen, a corpus luteum forms m both discharged and 

 atretic follicles. « 



