Protein Constituents of Spermatozoa 101 



NHo OH NH2 



N C X N C X HN CH 



I II CH I II CH I II 



HC C / H.,N— C C / OC CH 



^N^ ^NH ^N^ ^NH ^NH 



Adenine Guanine Cytosine 



(6-aminopurine) (2-amino-6-hydroxy- (2-hydroxy-6- 



purine) aminopyrimidine) 



O NH2 



II I 



/^\ ^^\ 



HN C— CH3 N C— CH3 



I II I II 



OC CH OC CH 



^NH ^NH 



Thymine 5-Methyl-cytosine 



(5-methyl-2 : 6-dihydroxy- 

 pyrimidine) 



following steps: acid hydrolysis which splits off purine and exposes 

 deoxyribose; transformation of deoxyribose into co-la evuUnic alde- 

 hyde; lastly, formation of a purple-coloured reaction product of 

 this labile aldehyde with fuchsin-sulphurous acid. The mechanism 

 of the Feulgen reaction as exhibited by the cell nuclei in histological 

 preparations, appears to be even more involved (Danielli, 1947; 

 Davidson, 1950). In cellular material, however carefully carried out, 

 the Feulgen reaction cannot be expected to yield results as accurate 

 and specific as the colour test with pure deoxyribonucleic acid. 

 Some of the difficulties inherent in the application of the reaction 

 as a staining method for sperm nuclei, have been pointed out by 

 Feulgen and Rosenbeck themselves, who noted that when fresh 

 smears of human semen were treated with Schiff 's fuchsin-sulphurous 

 acid reagent, the sperm-heads stained rather weakly, whereas 

 the middle-pieces and tails, though devoid of nuclear material, 

 stained strongly. This observation was followed by a demonstration 

 that the fuchsin-staining material present in the middle-piece and 

 tail is a lipid, 'plasmal', which can be distinguished from the 



