DIGESTIVE ACTION OF THE PANCREATIC JUICE. 343 



zymogen is found in small amount, 6 to 10 hours after a meal, in the 

 inner zone of the secretory cells, but, after 16 hours, it is very abundant 

 in the inner zone of the cells. It is soluble in water and glycerine. 

 Trypsiri is formed in the watery solution from the zymogen, and the 

 same result occurs when the pancreas is chopped up and treated 

 with strong alcohol (W. Kiihne). The addition of sodium chloride, 

 carbonate, and glycocholate, favours the activity of the tryptic ferment 

 (Heidenhain). 



[The following facts show that zymogen (?v/xjj, ferment), or, as it has 

 been called, trypsinogen, is the precursor of trypsin, that it exists in the 

 gland-cells, and requires to be acted upon before trypsin is formed. If 

 a glycerine extract be made of a pancreas taken from an animal just 

 killed, and if another extract be made from a pancreas which has been 

 kept for twenty-four hours, it will be found that an alkaline solution of 

 the former has practically no effect on fibrin, while the latter is power- 

 fully proteolytic. If a fresh and still warm pancreas be rubbed up with 

 an equal volume of a 1 per cent, solution of acetic acid, and then 

 extracted with glycerine, a powerfully proteolytic extract is at once 

 obtained. Trypsin is formed from zymogen by the action of acetic 

 acid (Heidenhain). There is reason to believe that trypsin is formed 

 from zymogen by oxidation, and that the former loses its proteolytic 

 power after removal of its oxygen. The amount of zymogen present 

 in the gland-cells seems to depend upon the number and size of the 

 granules present in the inner granular zone of the secretory cells.] 



Trypsin is never absent from the pancreas of new-born children (Zweifel), and 

 it may be extracted by water, which, however, also dissolves the albumin. 

 Kiihne has carefully separated the albumin and obtained the ferment in a pure 

 state. It is soluble in water, insoluble in alcohol. Pepsin and hydrochloric acid 

 together act upon trypsin and destroy it; hence it is not advisable to administer 

 trypsin by the mouth, as it would be destroyed in the stomach (Ewald, Mays). 



III. The action on neutral fats is twofold: (1) It acts upon fats 

 so as to form a fine permanent emulsion (Eberle). (2) It causes fats to 

 take up a molecule of water and split into glycerine and fatty acids: 

 Tristearin. Water. Glycerine. Stearic Acid. 



(C 57 H 110 6 ) + 3(H 2 0) = (C 3 H 8 3 ) + 3(0^0,). 



The latter result is due to the action of an easily decomposable fat- 

 splitting ferment (Cl. Bernard), also called steapsin. Lecithin is decom- 

 posed by it into glycero-phosphoric acid, neurin and fatty acids (Bokay). 

 After the decomposition is completed, the fatty acids are saponified 

 by the alkali of the pancreatic and intestinal juices. 



Emulsification. The most important change effected on fats in the small 

 intestine, is the production of an emulsion, or their sub-division into exceedingly 

 minute particles. This is necessary in order that the fats may be taken up by 



