206 PHYSIOLOGICAL CHEMISTRY. 



the acid combination is not in too great excess (CHITTENDEN and 

 CUMMINS). Organic acids act less disturbingly, and in the presence 

 of 0.2 p. m. lactic acid and the simultaneous presence of proteid, bile, 

 and common salt the digestion may indeed proceed more quickly 

 than in a faintly-alkaline liquid (LINDBERGER). Foreign bodies, 

 such as borax and potassium cyanide, may promote digestion, while 

 bodies such as mercuric, fenic and other salts (CHITTENDEN and 

 CUMMINS), or salicylic acid in large quantities (KUHNE), may act 

 preventively. The nature of the proteids is also of importance. 

 Unboiled fibrin is, relatively to most other albuminous bodies, dis- 

 solved so very quickly that the digestion test with raw fibrin gives 

 an incorrect idea of the power of trypsin to dissolve coagulated 

 albuminous bodies in general. An accumulation of digestion pro- 

 ducts tends to hinder the trypsin digestion. 



The Products of the Trypsin Digestion. In the digestion of un- 

 boiled fibrin a globulin which coagulates at -f- 55-56 C. may be 

 obtained as an intermediate product (HERRMANN). Moreover from 

 fibrin, as well as from other albuminous bodies, albumoses and 

 peptones, leucin, tyrosin and aspartic acid, a little ammonia 

 (HIRSCHLER), and a substance whose nature is not known and which 

 gives a beautiful purple-red liquid with chlorine or bromine water 

 in acid solution, have been obtained. When putrefaction has not 

 been entirely prevented numerous other bodies appear which will be 

 spoken of later in connection with the putrefaction process going 

 on in the intestine. In the trypsin digestion, in contrast to the 

 pepsin digestion, pure peptones, not precipitated by ammonium sul- 

 phate, are relatively easily and quickly formed. The peptone, 

 according to KUHNE consists entirely of antipeptone, and the above- 

 mentioned decomposition products, leucin and the others, are formed 

 by the decomposition of the hemipeptone. We will now consider 

 leucin and tyrosin decomposition products formed by the trypsin 

 digestion of proteids. 



Leucin, C 6 H 13 M) 2 , or AMIDO-CAPROIC ACID, C 5 H 10 (NH 2 )COOH, 

 besides occurring in the trypsin digestion of proteids, is derived 

 from the protein substances by their decomposition on boiling with 

 diluted acids or alkalies, by melting with alkali hydrates, and by 

 putrefaction. Because of the ease with which leucin and tyrosin 

 are formed in the decomposition of protein substances, it is difficult 



