312 THE PHYSIOLOGY OF REPRODUCTION 



nucleoprotein — one component of which is constant for the different 

 species and classes — the nucleic 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 sper- 

 matozoon. But such speculations are hardly justifiable until our 

 knowledge of the nucleus of the ovum is as complete as it is in the 

 cases of the male nucleus. At present we know practically nothing 

 of the chemical composition of the nucleus of the ovum. Nor is 

 it likely — and Miescher himself clearly recognised this — that the 

 intricate processes which are connected with fertilisation and heredity 

 are directly dependent upon such crude chemical facts as the per- 

 centage 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 living 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 concen- 

 tration of such groups with alternating 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. 304 shows, contains the group — 



I 

 NH=C— ^^H— CHa— . . . 



These facts suggest that this special arrangement of alternating 

 C and N atoms is the chemical expression of the specific function 

 of the nucleus, and that this arrangement plays a special part in 

 bringiag about the chemical processes which lead to growth and to 

 the new formation of living matter. 



In the case of the other organic compound present in every 

 nucleus, which contains iron in organic combination, the evidence 



' Kossel, "Einige Bemerkungen liber die Bildung der Protamine im 

 Thierkorip&v" Zeitsch. f. physiol. Ghem., vol. xliv., 1905. 



