Discussion 99 



the findings with the electron microscope have any bearing on the 

 possible demonstration of ketosteroids in the cat's testis. 



Fawcett: Yes, that is correct but I believe subsequent work has raised 

 some doubt as to the value of these reactions for the identification of 

 steroids. In human testis the results of the application of these histo- 

 chemical methods are particularly difficult to interpret because some 

 of the same staining reactions are given by both the acetone-insoluble 

 aggregations of pigment and the lipid droplets, and it would be sur- 

 prising if the pigment contained ketosteroid. 



Montagna: If one assumes that this series of tests reveals the sites of 

 ketosteroids, or hormone, or what have you, in the human testis one 

 must include (1) the primary spermatocytes and spermatogonia, and 

 (2) the Sertoli cells as sites of these substances. These elements give 

 reactions identical with those found in the Leydig cells. 



Fawcett: By electron microscopy, the Sertoli cells contain an abund- 

 ance of neutral fat droplets but pigment is relatively uncommon. We 

 have very rarely found either lipid or pigment in spermatogonia or 

 spermatocytes. 



Montagna: Judging only by the osmiophilia? 



Fawcett: Judging by their appearance in electron micrographs of 

 osmium fixed tissue. Osmiophilic pigment aggregations are easily dis- 

 tinguished from neutral fat in such preparations. 



