THE PANCREATIC JUICE. 137 



which is found in the animal world, and in its action on albumins is 

 fully capable of replacing pepsin when this is absent. Its digestive 

 power, moreover, is much more extensive than that of pepsin, and it 

 is further capable of decomposing albumins to amido-acids and 

 hexon bases. Its hydrolytic effect may thus be compared to the 

 action of strong mineral acids under the application of heat. This 

 explains also the fact that leucin and tyrosin are so frequently found 

 in the pancreatic juice. The extensive digestive activity of trypsin 

 is well shown when the gland is finely hashed and treated with a 

 large amount of chloroform- water, so as to guard against putrefac- 

 tive changes. When kept at a temperature of 40 C. autodigestion 

 rapidly takes place, and after several days it will be noted that while 

 trypsin is still present in its full activity, the other ferments have 

 disappeared. Together with the various albumins of the gland they 

 have apparently been digested by the more powerful ferment. 



While trypsin acts most energetically in feebly alkaline or neutral 

 solutions (0.25-1.0 per cent, of sodium carbonate), it is also capable 

 of digesting albumins in slightly acid media, providing that the 

 acidity is not due to the presence of a free mineral acid ; the diges- 

 tive process is under such conditions, however, much less active. 

 Free mineral acids rapidly destroy the ferment. Its optimum tem- 

 perature lies between 37 and 40 C. In neutral solution it is 

 destroyed at 45 C., while in feebly alkaline media, and especially 

 in the presence of albumoses and certain ammoniacal salts, it can be 

 heated somewhat higher without impairment of its digestive power. 



As in the case of pepsin, the digestive effect of trypsin is to a 

 certain extent dependent upon the amount of the ferment present, 

 and here as there the action of the enzyme ultimately ceases 

 when the digestive products accumulate beyond a certain amount. 

 Impure extracts can ba prepared, as has been pointed out, by 

 extracting the gland with glycerin after it has been left exposed to 

 the air. The purer forms, on the other hand, which can be obtained 

 according to Kiihne's method (see below), are insoluble in glycerin 

 and alcohol, but soluble in water. 



Of the chemical nature of trypsin little is known. In acid solu- 

 tion it is coagulated by heat, and, according to Kiihne, decomposed 

 into an albumin and peptone. An analysis of a fairly pure prepara- 

 tion has given the following results : carbon, 52.75 per cent. ; hydro- 

 gen, 7.51 ; nitrogen, 16.55 ; oxygen plus sulphur, 23.19 (Loew). 

 Its composition is thus very similar to that of the peptones, and it is 

 hence possible that, unlike the other digestive ferments which we 

 have thus far considered, trypsin may be an albuminous substance. 



Test for Trypsin. The test for trypsin resolves itself into the 

 demonstration of the presence of a proteolytic ferment which is 

 capable of digesting albumins in alkaline solution, with the ultimate 

 formation of amido-acids. To this end, the solution in question is 

 rendered alkaline with sodium carbonate to the extent of from 0.25 

 to 1.0 per cent. A small flake of fibrin is then added and an 



