86 Proceedings of the Eoijal Irish Academy. 



sort. At all events, it is quite certain that the evidence is strongly against 

 the view that the lutein grannies are or contain neutral fat. and there is 

 good reason for believing that these luteal granules are formed by a swelling 

 of the mitochondria of the follicle epitheliid cells. 



finally, with regard to the origin of the lutein cells, Cohn, w"ho has worked 

 at various types of mammals, including man. states : " . . . das die aus der 

 Theca interna hervorgegangenen Luteinelements mit der Histogenese der 

 grossen Corpus luteum-Zellen sensu strictori nichts zu thun haben . . ." 



Novak's figures as above mentioned, in agreement with Corner for the 

 sow, show that in the human the theea interna cells may swell up and 

 closely resemble lutein cells. It would be difficult to deny the possibility that 

 the two types of cells, follicle epithelial and thecal, which after all are both 

 derived from mesoderm, could both travel along the same line of difierentiation. 

 If the theea cell did not enter into the substance of the growing corpus 

 luteum with its "cast" as a connective cell too deeply branded upon ic, there 

 is good reason for supposing that it would be caught up in the train of the 

 developing luteal cells and caused to differentiate along their lines. In the 

 Platypus the "cast" of the theca interna cell is strong, it is never forgotten, 

 and the theca cells always remain connective, but in the higher mammals 

 the brand is not so strong and deep, and there seems to develop a remark- 

 able approximation in structure between the large glandular lutein cells and 

 the former thecal connective tissue cells. 



According to Coi-ner's latest results in the sow the pockets of cells 

 marked N in tig. 3 would presumably be clumps of theea interna cells. 

 Corner distinguished his luteal cells from the interna cells by means of the 

 vacuoles and rings in the former ; this I cannot do in the human. So far 

 as my examination of the human corpus has gone 1 have been led to 

 consider that the pockets N passed imperceptibly into the luteal cells L of 

 fig. 3. 



There are two courses for me to follow as the result of my own scanty 

 observations: one, to conclude that the luteal cells are of mixed origin; that 

 most of the theca interna cells so closely approximate in cytological arrange- 

 ment to the membrana cells that it is impossible to distinguish the two ; 

 and finally that the stellate cells are fibroid elements derived from free cells 

 of the theca externa. 



The other, which \ favour, is to look upon the stellate cells as theea interna 

 elements, and thus to deny the theory of mixed origin of lutein cells. Until 

 more material has been examined, and until Corner's material has been 

 viewed in the light thrown by Da Fano's method, we cannot be certain as to 

 the nature and origin of the stellate elements. 



