THE END-PRODUCTS OF ALBUMINOUS DIGESTION. 209 



the process of intestinal putrefaction. Of special interest is the fact 

 that while the primary albumoses of fibrin, as also the secondary 

 albumose-A, on further digestion with trypsin, give rise to the 

 formation of tryptophan, the secondary albnmose-B apparently does 

 not contain the chromogenic group. 



Hopkins and Cole have shown that tryptophan is skatol-amino- 

 acetic acid, and according to Ellinger it has either the formula : 



C.CH 2 CH.NH 2 .COOH 

 C 4 H 6 /VjH or C 



NH NH. 



To the presence of this complex in the albuminous molecule the 

 reaction of Adamkiewicz is due. 



On bacterial decomposition it yields indol, skatol, skatol carbonic 

 acid, and skatol acetic acid. 



With chlorine and bromine it yields at least three colored products, 

 the so-called protemochromes. Of the bromine products, one is a 

 bluish-violet substance, and contains about 35 per cent, of bromine ; 

 the second is a red body, with 27 per cent. ; and the third a brown 

 pigment, with the same amount of bromine. 



According to Nencki, a certain similarity exists in the percentage 

 composition of the red pigment with hsematoporphyrin, viz., biliru- 

 bin, and of the brown pigment with the so-called melanins. Tryp- 

 tophan, moreover, like hsematin and hsematoporphyrin, yields pyrrol, 

 hydrogen sulphide, methyl mercaptan, indol, and skatol on fusion 

 with tfaustic alkali. 



Test. The test for tryptophan and the isolation of the three 

 known pigments is conducted as follows : the digestive mixture 

 is acidified with acetic acid and treated with two and one-half times 

 its volume of saturated bromine- water. A beautiful reddish-violet 

 precipitate is thus formed, which increases on standing. After 

 twenty-four hours this is filtered off. On the further addition of 

 bromine-water the brown pigment separates out on standing. The 

 red pigment will be found in the violet precipitate, and can be iso- 

 lated as follows : the precipitate is first washed with water and then 

 extracted with dilute ammonia; this extract is precipitated with 

 acetic acid. The precipitate is separated from the brown filtrate, 

 redissolved in very dilute ammonia, again precipitated with acetic 

 acid, and washed with water. It is then extracted with amyl 

 alcohol ; this dissolves the red body. The alcohol is evaporated 

 off at 40 C., the residue dried at 106 C., and finally washed with 

 ether. The violet pigment is obtained on further extraction of the 

 violet precipitate with a little stronger solution of ammonia than in 

 the first instance. The substance is precipitated with acetic acid, 

 well washed with water, and extracted with 95 per cent, alcohol. 

 The alcoholic extract is evaporated to dryness at 40 C., the residue 

 dried at 106 C. and washed with petroleum ether. 

 H 



