CHEMICAL BASIS OP THE ANIMAL BODY. 89 



dissolved in very weak caustic soda, precipitated by hydrochloric acid 

 and washed with water and alcohol. Prepared by the above methods, 

 nuclein is an amorphous substance, rich in phosphorus, which is set 

 free as phosphoric acid when it is boiled with alkalis. At the same 

 time some form of proteid usually makes its appearance as also do the 

 crystalline substances of the xanthin series, guanin (?) and hypo- 

 xanthin when the nuclein is heated with dilute mineral acids instead 

 of alkalis 1 . It appears however that the absolute and relative amount 

 of the above possible products of its decomposition varies with the 

 source from which the nuclein is obtained. 



Under the name ' adenin ' Kossel has more recently described a new base which 

 he obtained by the decomposition of nuclein from yeast-cells with dilute sulphuric 

 acid and heat 2 . It is crystalline, readily soluble in warm water and caustic alkalis, 

 and when treated with nitrous acid yields hypoxanthin (See below.) 



C 5 H 5 N 5 + H 2 = C 5 H 4 N 4 + NH 3 . 



When egg- or serum-albumin is precipitated with metaphosphoric acid, a phos- 

 phorised substance is obtained which exhibits many of the reactions characteristic 

 of nuclein 3 . It does not however yield any of the xanthin bases when treated with 

 acids 4 . 



Nucleo-albumins. 



While the nuclei may be regarded as composed principally of the 

 somewhat unsatisfactorily characterised nucleins, there is evidence of 

 the existence 5 of closely allied substances to which, since they appear 

 to be a compound of nuclein and a proteid, the name nucleo-albumin 

 has been given. Our knowledge of these substances is as yet rudi- 

 mentary and imperfect, and subsequent investigation must decide their 

 real nature and their relationship to the nucleins. 



The more characteristic reactions of the nucleo-albumins may be 

 stated as follows. Soluble in very dilute alkalis they are readily 

 reprecipitated by acetic acid and the constancy in properties of the 

 product obtained by repeated solution and precipitation seems to show 

 that they are not mere mixtures of nuclein and proteid. Their 

 behaviour towards alkalis and acetic acid is such as to lead to an 

 easy confusion with the mucins. When digested with pepsin they 

 yield peptones and albumoses and a phosphorised residue which is in 



1 Kossel, loc. cit. Also Zt. f. physiol. Chem. Bd. v. (1881), Sn. 152, 267; Bd. 

 vm. (1884), S. 404. 



2 Ber. d. d. chem. GeselL 1885, Sn. 79, 1928. Zt. physiol. Chem. Bd. x. (1886), 

 S. 250. Schindler, Ibid. Bd. xm. (1889), S. 432. Bruhns, Ibid. Bd. xiv. (1890), S. 

 533. 



3 Liebermann, Ber. d. d. chem. GeselL 1888, S. 598. PMger's Arch. Bd. XLVII. 

 (1890), S. 155. 



4 Pohl, Zt.f. physiol. Chem. Bd. xm. (1889), S. 292. 



5 Worm-Muller, Pfliiger's Arch, Bd. vm. (1874), S. 194. 



