ORIGIN OF THE CORPUS LUTEUM 125 



the connective tissue of the corpus is contributed also by the 

 theca externa, which is drawn inward in places by the folding of 

 the follicular walls. O'Donoghue ('12, '14, '16) has given a con- 

 firmation of Sobotta's views for the marsupials (which I believe 

 were first studied by Sandes ('03), whose paper was not acces- 

 sible to me). Strakosch ('15) is the last to repeat the Sobotta 

 theory in its original purity, basing his statements upon the 

 human ovaries which were used by Robert Schroeder in his 

 study of the time relation between ovulation and menstrua- 

 tion ('14). 



Van der Stricht's belief that the theca interna cells are not con- 

 verted into fibroblasts, but remain in the corpus luteum, no 

 longer distinguishable from other lutein cells, found support in 

 the study of L. Loeb ('06) upon the guinea-pig. The specimens 

 were collected in a series dated from copulation without study of 

 the ova. The theca interna cells, after a few hours, could no 

 longer be distinguished from the granulosa lutein cells. This 

 work is open to the criticism that haematoxylin and eosin (the 

 only staining combination used) do not accentuate differences 

 between cells of the types met with in this problem. In 1908 

 Van der Stricht himself repeated his ideas as the result of re- 

 searches upon the ovaries of dogs, carefully checked up by exam- 

 ination of the ova, and in 1912 he repeated his findings in the bat. 



A somewhat different view has found exposition in the very 

 careful work of Volker ('05) upon Spermophilus citellus, a Euro- 

 pean marmot allied to the gophers of the western United States. 

 The ova and embryos were recovered and examined in all cases, 

 and there appears to have been a sufficient number of stages, 

 though the author does not state the number of specimens studied. 

 The theca interna cells were found to persist unchanged between 

 the granulosa and the theca externa, even until the end of preg- 

 nancy. The few spindle-cells found in the fully formed corpus 

 luteum are said to proceed from the theca externa. Practically 

 the same view is presented in the thesis of Niskoubina ('09), who 

 worked on the rabbit, but does not give an account of the methods 

 used. Cohn ('09) studied the human ovary, but appears to 

 have seen no really young stages. His descriptions agree with 



