THE PANCREATIC JUICE. 149 



appears as such, and only as such. With one of milk and bread the 

 zymogen only appears, and must first be activated by the enteric 

 juice. The aruylolytic ferment, on the other hand, is not influenced 

 in this manner, and is always secreted as ferment. With lipase 

 conditions resemble those in the case of trypsin. With a diet of 

 carbohydrates and much fat the zymogen appears, while with a meat 

 diet the ferment is furnished directly (Lintwarew). 



Of the chemical composition of the zymogens we know little, but 

 it appears that they are of an albuminous nature and of a more com- 

 plex composition than the ferments themselves. On decomposition 

 trypsinogen is said to yield the corresponding ferment and an un- 

 known albuminous substance. Of the origin of the zymogens, and of 

 the manner in which they are produced in the cells, we know nothing. 



Trypsin. Trypsin is the most important proteolytic ferment 

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

 is fully capable of replacing pepsin when this is absent. Its diges- 

 tive power, moreover, is much more extensive than that of pepsin, 

 as it is capable of decomposing albumins to amino-acids. Its hydro- 

 lytic effect may thus be compared to the action of strong mineral 

 acids under the application of heat. It is to be noted, however, 

 that albuminous material which has been first subjected to the action 

 of pepsin-hydrochloric acid and then to trypsin is more rapidly and 

 more completely hydrolyzed than when acted upon by trypsin alone. 

 The extensive digestive activity of trypsin is well shown when the 



fland is finely hashed and treated with a large amount of chloro- 

 )rm-water, so as to guard against putrefactive changes. When 

 kept at a temperature of 40 C. autodigestion rapidly takes place, 

 and after several days while trypsin is still present in its full activ- 

 ity, 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. 



One of the most important characteristics of trypsin is its inability 

 to transform firmly combined nitrogen into the loosely combined 

 form. On long-continued tryptic digestion of serum-albumin it 

 will be noted that the amount of nitrogen which can be obtained on 

 distillation with magnesia is essentially the same as the amount that 

 can be obtained on hydrolysis with acids. 



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

 certain extent dependent upon the amount of the ferment present, 



