102 The Biochemistry of Semen 



nucleoprotein of the sperm-head by its solubiUty in ethanol. Similar 

 observations with animal sperm were later reported by other investi- 

 gators. There is no doubt, however, that if carried out properly and 

 under conditions which eliminate interference from other fuchsin- 

 staining substances, the Feulgen nucleal reaction can be made 

 specific for the sperm nucleus. Several authors have stressed the 

 fact that the base and the posterior region of the sperm-head stains 

 particularly strongly (Marza, 1930; Wislocki, 1950; Friedlaender 

 and Fraser, 1952). 



Although present in the sperm nuclei of all species, the composi- 

 tion of deoxyribonucleic acid varies somewhat from one species to 

 another, with regard to the proportion of the various purine and 

 pyrimidine bases. But within any given species, all body cells, includ- 

 ing the spermatozoa, seem to yield on purification the same nucleic 

 acid, that is one with the same molar ratio of adenine, guanine, 

 cytosine and thymine. In the species so far examined, the ratio of 

 adenine to thymine, of guanine to cytosine, and of total purines to 

 total pyrimidines, was shown to equal unity. 



The results of the analysis of bases in deoxyribonucleic acid from 

 ram spermatozoa are shown in Plate V. The spermatozoa were dis- 

 integrated mechanically and suspensions of washed, tail-free sperm- 

 heads were prepared (Mann, \95\b). Nucleic acid was separated 

 from the nuclear proteins of the sperm-heads by the chloroform- 

 octanol treatment, hydrolysed with formic acid, and the liberated 

 bases separated on paper chromatograms by Wyatt's method, using 

 as solvent an aqueous solution containing 65% /^(^propanol and 

 2N-HC1. The bases set free by acid hydrolysis and determined 

 spectrophotometrically according to Markham and Smith (1949) 

 were: guanine, adenine, cytosine and thymine in a molar ratio of 

 0-91 : M3 : 0-86 : 110. In addition, there was a small amount of 

 methylcytosine which in Plate V is only just visible as a faint ultra- 

 violet-absorbing band below cytosine; the molar ratio of cytosine 

 to methylcytosine was 1 : 005. 



Deoxyribonucleic acid (Na-salt) of human sperm was studied by 

 Chargaff and his colleagues (Chargaff, Zamenhof and Green, 1950; 

 ChargafF, 1951a, b)\ it contains 16% nitrogen and 8-9% phosphorus 

 (Zamenhof, Shettles and Chargaff, 1950); the specific viscosity of a 

 0-135% solution in water equals 7-0, and the sedimentation constant 



