504 ANDREW T. RASMUSSEN 



The role of the large amount of fatty material which may 

 accumulate in these cells in certain animals — though rather 

 scarce in others, notably the pig — is of course equally obscure. 

 The chemical nature of the large globules in the interstitial 

 cells of the cat has been investigated especially by Whitehead 

 ('12 b), who concluded that they are a mixture for the most part 

 of phosphatid lipoid but that cholesterinesters and neutral fats 

 are probably also present. The views that this lipoid is the 

 material out of which the internal secretion is made (Loisel '02), 

 that it is the internal scretion (Ganfini, '02), etc., need to be 

 supported by many more facts. The effects of lipoid extracts of 

 the testis, such as those reported by Iscovesco ('13), are, of 

 course, very suggestive that the lipoid is an active agent. 



In this connection we may recall the view of Plato ('97), that 

 this fatty material passes through the walls of the tubules into 

 the Sertoli cells to be used as food for spermatogenesis. For 

 this reason he termed the interstitial cells 'Trophische Hiilf- 

 zellen.' Lenhossek ('97) entertained somewhat the same idea 

 and Regaud ('01) presented evidence of such a passage of sub- 

 stance from the interstitial cells to the Sertoli cells. Plato's 

 idea was strictly opposed by Beissner ('98) and in general this 

 passage of material through the walls of the tubules from the 

 interstitial cells has not been supported by the later investi- 

 gators. Friedmann ('98), however, suggested .that the pigment 

 in summer and the fat in winter, in the case of the toad, es- 

 pecially, serve as the chief sources of nutrition for the proc- 

 esses going on in the tubules. Herxheimer concluded that in 

 individuals not yet sexually mature, the fat is mostl}^ found in 

 the interstitial cells and is reserve material for the growing 

 testis, while in the sexually mature the fat is mostly found in the 

 tubuli contorti where it serves as reserve material for the de- 

 velopment of spermatozoa. Hanes ('11), however, associates 

 the fat storage with the Sertoli cells. 



Of historical interest, at least, is also the conclusion of von 

 Bardeleben ('97) that the interstitial cells of the testis are 

 young Sertoli cells which can pass through the walls of the 

 tubules and replace worn out Sertoli cells. Goldmann ('09), 



