264 TRYPTOPHAN. [BOOK II. 



which has been kept for some time, unless putrefaction sets in, when 

 it ceases. Claude Bernard observed that when, through putrefaction, 

 the chlorine reaction could no longer be obtained, if the liquid were 

 precipitated with lead acetate, the filtrate freed from lead by dilute 

 sulphuric acid, and the second filtrate were treated with nitric acid 

 containing nitrous acid, a red colour was produced ; this he believed 

 to be caused by the same body which had originally caused the rose 

 colouration with chlorine. 



Kiihne 1 proved this view to be untenable, the nitric and 

 nitrous acid reactions being due to the formation of indol, which 

 could be separated by distillation. Kiihne 'shewed that the very 

 different substance which exhibits the chlorine reaction also gives a 

 red or violet colour when treated with bromine water, and since he 

 introduced its use bromine water has generally been employed, for 

 this purpose, in the laboratory instead of chlorine water. 



It is mainly due to the researches of Kuhne that we have become 

 acquainted with the fact that tryptophan, as we shall henceforth 

 designate it, is produced not only as one of the products of the 

 pancreatic decomposition of proteids, but is likewise to be found 

 (though it is rapidly destroyed and disappears) as a constant product 

 of the splitting-up of the albuminous molecule, in whatever manner 

 this may be brought about. Kiihne is of opinion that it is one of 

 the products of the decomposition of the hemi-moiety of the molecule. 



Thus it is one of the products of decomposition when the 

 proteids are treated by Schiitzenberger's process 2 , as well as when 

 they are boiled with 5 per cent, sulphuric acid, though in the latter 

 case the reaction is slight, and the body which occasions it rapidly 

 disappears 3 . 



Chemical Tryptophan is slightly soluble in alcohol, ether, and 



and physical chloroform (Krlikenberg). It is more readily soluble 

 properties of i n am yl alcohol, which may be employed to effect its 

 tryptophan C separation (Hemala 4 ). In the latter case the reaction 

 should be obtained by the use of chlorine water, as 

 bromine is soluble in amyl alcohol, and imparts to it a yellow colour. 

 The tinctorial intensity of tryptophan is very great, so that 

 solutions which give an intense violet colouration with chlorine, 

 furnish but a small quantity of the colouring matter. According to 

 Kriikenberg, chlorine or bromine do not cause the colour reaction of 

 tryptophan by an oxidising action, but by actually entering into com- 

 bination with the body. This author found that tryptophan is diffu- 



1 Kiihne, Ueber Indol aus Eiweiss,' Ber. d. deutsch. chem. Gesellschaft, Vol. vm. 

 (1865), p. 206. 



2 Neumeister, ' Ueber die Keactionen der Albumosen und Peptone,' Zeitschrift fiir 

 Biologic, Vol. xxvi. (1890), see p. 332. 



3 Neumeister, loc. cit. See note to page 329. 



4 Rich. Hemala, ' Zur Kenntniss der in der chemischen Physiologie zur Anwendung 

 gekommenen Nitroprussid-reactionen ' in Krukenberg's Che.mische Untersuchungen zur 

 wissenschaftlichen Medicin, 2tes Heft, June 1888, p. 118. 



