The Biological Significance of the Sertoli Cells. 163 



veloped in cryptorchids, one can conclude, firstly, that the testicle 

 does furnish an internal secretion to the organism, and, secondly, 

 the secretion is elaborated either by the Sertoli cells or interstitial 

 cells. It is the purpose of this note to bring forward evidence 

 which has come to light in a study of normal and cryptorchid 

 testicles of the pig, showing that the Sertoli cells have the very 

 definite function of furnishing nutriment, especially fat, to the 

 developing sperm-cells. Benda, Peter, Grobben, v. Ehner and 

 others have concluded on morphological grounds that the Sertoli 

 cells are nutritive cells; evidence from the physiological side has 

 been lacking. 



Fat is a constant physiological constituent of Sertoli cells. In 

 the cryptorchid testicle this fat is seen to be greatly increased in 

 amount, and ether-alcohol extractions show that whereas 18.3 per 

 cent, of the dried weight of the normal testicle is fatty matter, 30 

 per cent, of the dried weight of the cryptorchid testicle is composed 

 of fat. The sperm-forming cells are absent from the cryptorchid 

 testicle, hence the fat accumulates in the Sertoli cells. Miescher 

 has found that 58 per cent, of the cytoplasm of the salmon sperm 

 is extractable by alcohol-ether. 



In the normal testicle large droplets of fat are found in the 

 base of the Sertoli cells, and as one proceeds centralward the fat 

 in these cells is found more and more finely divided, lying in close 

 contact with the spermatids, which also contain fat droplets. 



Applying Marchi's stain to the testicle, it is found that only 

 the large peripheral droplets reduce osmic acid; the smaller cen- 

 trally disposed droplets remain uncolored. The explanation is 

 that phosphorized-fat when treated with potassium bichromate 

 loses its power of reducing osmic acid; neutral fats are not thus 

 changed. This reaction is not seen in the fat of the cryptorchid 

 testicle. 



