570 SWALE VINCENT 



a typical glandular formation. Its blood supply is abundant, and the 

 cells are polygonal in shape and contain granules. These are of various 

 kinds, as indicated by their staining reaction (O'Donoghue, Rasmussen). 

 There is an abundant chondrioma and enclosures of a lipoid character, 

 siderophil protoplasm, and distinctly polychromatic, large, round nuclei. 

 The chondrioma is made up of chondrioconta and mitochondria. It un- 

 dergoes important modifications in the course of the evolution of the 

 cell. The granulations, at first few, increase in the later stages; the 

 fatty products are the result of a chemical change in the mitochondrial 

 substance. The lipoid enclosures probably represent the products of secre- 

 tion (Athias). 



The function of the interstitial cells is completely unknown. No 

 discussion of this subject can be useful which ignores the fact that the 

 tissue appears to be absent in large numbers of animals. It may be that 

 a thorough investigation of the occurrence or non-occurrence of the tissue 

 in question in a very large number of species might throw considerable 

 light on the question, especially if due account were taken of any pe- 

 culiarities in the cyclic function of the reproductive organs in the different 

 types. It is not easy to suggest any direct experimental work which 

 might be expected to elucidate the problem. 



In Marshall's (/) book on the physiology of reproduction very little is 

 said about the interstitial celle. The author calls attention to the fact 

 that Miss Lane-Claypon has shown that the cells increase in size during 

 gestation. She suggests that the interstitial cells produce a secretion of 

 the same kind as that manufactured by the corpus luteum. 



iOf late years a great deal has been written about the internal secre- 

 tion of the interstitial cells, lut no hypothesis has been put forward 

 which has much evidence in its favor. No mass of cells which is not 

 muscular or nervous or obviously supporting cells and which is not 

 in connection with a duct can at the present time escape the charge of 

 furnishing an internal secretion. 



In 1905 Marshall and Jolly (a) concluded that heat in animals is not 

 caused by a secretion of the corpus luteum, but probably by means of 

 an influence exercised by the interstitial cells. This suggestion was re- 

 peated in 1911. The experiments of Lacassagiic do not support this hy- 

 pothesis. Heat occurs in animals, even when all the secreting elements 

 of the ovary have been destroyed. 



The view which is now held by the majority of writers is that the 

 interstitial cells preside over the nutrition of the reproductive organs and 

 are responsible for the appearance of the secondary sexual characters. 

 We have seen above (p. 552) that extirpation of the ovary interferes with 

 the development of these characters and gives rise to atrophy of the uterus. 

 Successful transplantation may have the effect of maintaining the normal 

 condition. As we have seen (p. 556), Steinach finds that, if ovaries are 



