176 PHYSIOLOGICAL CHEMISTRY. 



ence of indol formed. The tube containing the hydrochloric acid kept 

 several hours at 40 C does not show the effect of digestion, indicating 

 that an acid medium does not suffice for the converting activity of the 

 pancreatic ferment. A minute trace of acid, below about 0.05 per cent, 

 does not appear to check the action. 



To readily recognize the final products of the pancreatic digestion of 

 proteins it is necessary to start with larger quantities of materials than 

 are given above. 



An experiment made as above shows at first digestion and 

 finally bacterial putrefaction as disclosed by the indol odor. 

 A better idea of some of the products formed in digestion may 

 be secured by operating as follows : 



Ex. Mince 50 gm. of fresh fibrin and 25 gm. of pancreas, mix and 

 cover the mixture with 250 cc. of alkaline thymolized water, the thymol 

 being added to check too rapid putrefaction. Keep the mixture at 40 

 two or three days in a closed vessel, the mass being frequently shaken or 

 stirred. At the end of the digestion the alkali of the mixture is neutral- 

 ized with a faint excess of acetic acid, after which it is boiled in a porce- 

 lain dish and filtered. Some of the fibrin may remain and there will 

 always be some fat to separate by the filtration. The filtrate is used for 

 the identification of important products, some of which are readily recog- 

 nized, while others are not. 



PRODUCTS OF DIGESTION. 



Tryptophane. This name is given to a peculiar product 

 or mixture of products found in a pancreatic digestion like the 

 above. It is characterized by giving a marked violet red color 

 when mixed with a little chlorine water or bromine water. 

 The composition of the tryptophane is not yet known, but on 

 treatment with alkalies at the fusion temperature a mixture 

 of several complex aromatic products, including indol and 

 pyrrol, is obtained. Quite recently the name tryptophane has 

 been given to one of the constituents of this mixture which 

 has the formula C^H^NaC^ and which has been shown to be 

 skatol-a-aminoacetic acid. 



In a concentrated solution the addition of bromine or chlor- 

 ine produces a precipitate. This may be redissolved only in 

 a very considerable excess of water. The solution does not 

 yield the protein reactions at all, from which it follows that 



