I3 2 PHYSIOLOGICAL CHEMISTRY. 



Action may be observed however in neutral solution and even 

 in presence of a trace of acid. In its hydrolysis of proteins 

 trypsin goes farther than pepsin. The action of the latter, 

 under ordinary conditions, ends with the production of albu- 

 moses and peptones, while the pancreatic enzyme carries the 

 splitting process to the extent of producing a number of com- 

 paratively simple amino acids, and the hexone bases. In this 

 respect the behavior of the trypsin is comparable with that of 

 weak sulphuric acid when heated with the protein bodies. As 

 already pointed out in a former chapter this acid resolves the 

 proteins into complexes which may be considered as the con- 

 stituent groups of the large molecule. The trypsin digestion 

 may be carried far enough to leave products which fail to show 

 more than a very faint biuret reaction. This reaction, it will 

 be remembered, persists as long as anything having the charac- 

 teristics of the original protein substance remains. From all 

 this it is evident that the trypsin is a hydrolyzing agent of 

 marked power. 



Of the real nature of the enzyme nothing is known. It has 

 never been isolated in a condition of even approximate purity. 

 The pancreatic extracts of the market contain the enzymes 

 acting on fats and carbohydrates as well, in addition to a very 

 large amount of other matter. The active ferment is very 

 soluble in water and in dilute glycerol or dilute alcohol, but in 

 strong alcohol or glycerol it is insoluble. In presence of weak 

 hydrochloric acid trypsin is quickly digested or destroyed by 

 pepsin, and at temperatures much above 50 C. it soon becomes 

 inactive. The temperature optimum is probably about 40 to 

 45, in weak alkaline solution, but the statements in the litera- 

 ture on this point are somewhat discrepant. 



THE UREA FERMENTATION. 



Urease an* Other Ferments. Urine exposed to the air 

 soon becomes alkaline and the presence of ammonia is easily 

 shown. This behavior is due to the formation of ammonium 

 carbonate fro,m the urea by a reaction which may be expressed 

 in this way : 



