296 THE PHYSIOLOGY OF REPRODUCTION 



The non-nitrogenous part is spKt up further according to the 

 following equation : — 



Cj^H^jOsoPi + 4H2O + 20 = 4C6Hi20e + 4HPO3. 



Hexose Metaphosphoric 

 pugar. acid. 



In other words, the " skeleton " of the nucleic acid molecule 

 is formed by four molecules of metaphosphoric acid combined 

 with four molecules of a sugar : ^ a tetraglyco-metaphosphoric 

 acid, similar to the glycerophosphoric acid which forms the 

 " skeleton " of phosphorised fatp. In the nucleic acid molecule 

 this glycophosphoric acid is combined with four different nitro- 

 genous substances, of which two are pyrimidine derivatives and 

 two are purine derivatives.^ 



It is an interesting fact that while nucleic acid prepared 

 from ripe spermatozoa does not contain pentoses, these sub- 

 stances are stated to be present in the nucleic acid of the testis 

 of the bull,^ which represents the acid constituent of the nuclei 

 of the sexual element in the various stages of their development. 

 Since the statement of the presence of a pentose in the nucleic 

 acid from the testis of the bull is based only on the preparation 

 of an osazone, further investigation on this point and analytical 

 data are necessary before it can be accepted. 



The observations of Miescher * allowed of a quantitative esti- 

 mation of the amount of nucleic acid and protamine present in 

 the head of the spermatozoa of the salmon after the fat had 

 been removed. 60'5 per cent, of nucleic acid was found to be 

 combined with 35 '5 per cent, of salmine, so that 96 per cent, of 

 the head of the spermatozoon consists of protamine nucleate. 

 This protamine nucleate is, however, not of the same nature 

 in different parts of the head, the outer layer containing a basic 

 nucleate rich in protamine, while the inner portion is composed 

 of an acid nucleate poorer in protamine. 



' The sodium-salt of a tetraphosphorio acid can be prepared by fusing 

 together the sodium metaphosphate and pyrophosphate (Kraut and Uelsmann, 

 lAebig's Annalen, vol. cxviii., 1861). The organic derivatives of this base 

 have not yet been studied. 



" For a slightly different view of the constitution of nucleic acid, see 

 Burrian in Ergehnisae dcr Physiologie, vol. v., Hoc. cit. 



' Steudel, "tjber die Kohlenhydratgruppe in der Nukleinsanre," Zeit- 

 aahrift f. physiolog. Chemie, vol. Ivi. , 1908. 



* Miescher, Histochemische Arbeiten. 



