THE PRODUCTS OF TRYPTIC DIGESTION. 193 



(4) C 6 H 3 CO.NH 2 .C.C 6 H 5 .CH.COOH'+ H 2 O = 



Benzoyl-amido-ciimamic acid. C 6 H 5 .CO.NH 2 + C 6 H 5 .CH 2 .CO.COOH 



Beiizamide. Phenyl-pyro-racemic 

 acid. 



Method. The decomposition of the albumins (gelatin) is effected 

 by prolonged boiling with dilute sulphuric acid 25 per cent, solution. 

 The excess of acid is removed with plumbic carbonate. The filtrate 

 is concentrated, freed from any tyrosin that may have separated out, 

 and then benzoylated with benzoyl chloride in the presence of 

 sodium hydrate. Care should be had that the reaction of the solu- 

 tion is constantly alkaline during this process. The hippuric acid 

 is then extracted with acetic ether. The dried substance is now 

 treated with three molecules of acetic anhydride, one molecule of 

 sodium acetate, and one molecule of benzaldehyde. The mixture is 

 heated on a water-bath for half an hour. The condensation-produce 

 is then treated with water and gently warmed. The oil that sepa- 

 rates out is dissolved in hot alcohol and allowed to cool. The lacti- 

 mide then crystallizes out, and can be recognized as follows: the 

 substance is heated with a strong solution of sodium hydrate 

 until a distinct odor of ammonia is noticed. This is due to 

 the decomposition of the benzamide. On acidifying the solution 

 the phenyl-pyro-racemic acid separates out and can be readily ex- 

 tracted by shaking with ether. One portion of the ethereal extract 

 is treated with a dilute solution of the sesquichloride of iron, when 

 on agitation the watery layer assumes a dark-green color, which 

 gradually changes to a characteristic yellow. The other portion is. 

 treated with an ethereal solution of phenylhydrazin, which leads to the 

 separation of the hydrazon of phenyl-pyro-racemic acid. After wash- 

 ing with ether this may be identified by its melting-point 161 C- 



As regards the general properties of glycocoll and its preparation 

 as such, see pages 87 and 259). 



Tryptophan. This substance is apparently always formed when 

 the tryptic digestion of the albumins has extended beyond the forma- 

 tion of albumoses. As its presence among the various digestive 

 products is easily recognized, it is thus possible to ascertain whether 

 the destruction of the albuminous molecule has extended to the 

 formation of amido-acids, without testing for these directly. Like 

 the amido-acids, it is also formed during the hydrolytic decomposi- 

 tion of the albumins with bary to- water, and likewise results during 

 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 albumose-B' at least appar- 

 ently does not contain the chromogenic group. 



The substance itself is colorless, and is hence also spoken of as 

 proteinochromoc/en. "With chlorine and bromine it yields at least 

 three colored products, the proteinochromes, and it is hence supposed 

 that several varieties of the chromogen may also exist. Of the 

 chemical nature of both, however, but little is known. While 



