CHAP. III.] RELATION OF HYPOXANTHINE TO ADENINE. 263 



Subsequently, Kossel found that when the pancreas 



Kossei's dis- j g boiled for three . or four hours with a very dilute 



adenine. sulphuric acid (one part of concentrated sulphuric acid 



in four parts of water) a base is set free, adenin, which is 



a polymer of HCN, and which has the composition C 5 H 5 N 5 4- 3H 2 0. 



This base, he has shewn, is formed in the first instance from 

 nuclein, and the bypoxanthine which is obtained by decomposing 

 nuclein is derived from adenin 1 . When the latter base is treated 

 with nitrous acid, hypoxanthine is formed. 



C 5 H 5 N 5 + HN0 2 = C 5 H 4 N 4 + N 2 + H 2 O. 



Adenin appears to be an amido-hypoxanthine and to bear the same 

 relation to it that guanine bears to xanthine. 



After an examination of the facts adduced, the conclusion is 

 inevitable that the so-called xanthine bodies do not originate by the 

 profound decomposition of the albuminous or albuminoid bodies 

 under the influence of trypsin, but are the products of the decom- 

 position of nucleins, a decomposition which appears to occur with 

 great ease under a variety of circumstances capable of effecting the 

 hydrolytic splitting-up of organic compounds. 



Tryptophan. 



We shall by this name 2 designate a substance as yet known only 

 by the reactions which it exhibits when its solutions are treated with 

 chlorine or bromine water, but which may be found among the 

 products of decomposition, of the albuminous molecule, in whatever 

 manner this may be brought about. 



History. Tiedemann and Gmelin 3 observed for the first time 



that the pancreatic juice of the dog assumes a rose-red colouration 

 when it is treated with chlorine water, and assumed that this reaction 

 was characteristic of the pancreatic secretion. Claude Bernard 4 , 

 however, shewed that the perfectly fresh and normal pancreatic juice 

 does not exhibit the reaction, but that it is obtained with the juice 



1 Kossel, 'Ueber das Adenin,' Zeitsch. f. phys. Chem., Vol. x. (1886), pp. 250 



2 The name Tryptophan has been suggested by Neumeister as indicating the origin 

 of the body in the decomposition of proteids. It is derived from Opvirro/j-ai, to be 

 broken, and (paivu, to bring to light. 



K. Neumeister, ' Zur Physiologic der Eiweissresorption und zur Lehre von den 

 Peptonen,' Zeitschrift fur Biologic, Vol. xxvu. (1890), pp. 309373; see, concerning 

 Tryptophan, p. 345 (note). 



E. Stadelmann has applied the term Proteinochromogen to the same substance. 

 Surely it is scarcely appropriate to apply a name implying that it is the cause of the 

 colours displayed by the proteids (?), to a body which is but an unknown product of 

 their decomposition. 



3 Tiedemann and Gmelin, Die Verdauung nach Versuchen.' Heidelberg, 1831. 



4 Claude Bernard, ' Memoire sur le Pancreas.' Comptes Rendus, Supplement, 

 i. (1856), pp. 403409. 



