THE PHYSIOLOGY OF REPRODUCTION 



acid. The other more or less basic component varies widely 

 for the different classes of Vertebrates, and shows minor 

 variations for the different species in any one class. Besides 

 this nucleoprotein, another organic substance, containing iron in 

 organic combination, is present in very small amounts. 



It is perhaps natural that attempts should have been made 

 to associate these different substances with the functions of the 

 spermatozoon. But such speculations are hardly justifiable 

 until our knowledge of the nucleus of the ovum is as complete 

 as it is in the case of the male nucleus. At present we know 

 practically nothing of the chemical composition of the nucleus 

 of the ovum. Nor is it hkely — and Miescher himself clearly 

 recognised this — that the intricate processes which are con- 

 nected with fertilisation and heredity are directly dependent 

 upon such crude chemical facts as the percentage of arginine 

 or serine, or the composition of nucleic acid. 



We are on safer ground when we consider the head of 

 the spermatozoon simply as a typical nucleus, and when we 

 draw deductions from the chemical composition of the nuclear 

 material of the spermatozoon, as to the functions of the nucleus 

 generally. 



It is a very suggestive fact that the nucleus — that is to say, 

 that part of the cell which is pre-eminently concerned in the 

 new formation of Uving material — is distinguished by the presence 

 of pyrimidine and purine derivatives, substances rich in nitrogen, 

 which are arranged in a chain of alternating C and N atoms. ^ 

 In the spermatozoon, where the nuclear function finds its 

 most pronounced expression, we find, at least in the case of 

 the fishes, a further concentration of such groups with alternat- 

 ing C and N atoms. For, besides the pyrimidine and purine 

 derivatives of the nucleic acid part, there is also present the 

 basic protamine part. As has been explained above, this part 

 is composed largely of arginine, which, as the formula given 

 on p. 290 shows, contains the group — 



NH, 



I 

 NH = C-NH-CH2-. . . 



^ Kossel, " Binige Bemerkungen iiber die Bildung der Protamine im 

 Thierkorper," Zeitachrift f. phys. Chemie, vol. xliv., 1905. 



