z88 TEXT-BOOK OF PHYSIOLOGY. 



Physiologic Action of Pancreatic Juice. Experimental investi- 

 gations have demonstrated the fact that pancreatic juice is the most complex 

 in its physiologic action of all the digestive fluids. By virtue of its contained 

 enzymes, pancreatic juice acts: 



1. On starch. When normal pancreatic juice or a glycerin extract of 

 the gland is added to a solution of hydrated starch, the latter is speedily 

 transformed into maltose, passing through the intermediate stage of dextrin. 

 The process is in all respects similar to that observed in the digestion of 

 starch by saliva. Pancreatic juice, however, is more energetic in this respect 

 than saliva. The enzyme which effects this change is termed amylopsin. 

 When the starch which escapes salivary digestion passes into the small 

 intestine and mingles with pancreatic juice, it is very promptly converted into 

 maltose by the action or in the presence of this enzyme. 



2. On protein. When protein compounds are subjected to the action 

 of pancreatic juice, they are transformed into peptones which do not differ 

 in essential respects from those formed by the action of gastric juice. The 

 intermediate stages, however, are believed to be somewhat different. The 

 enzyme which effects this change is termed trypsin. 



When fibrin, for example, is added to trypsin in a solution rendered 

 alkaline by sodium carbonate, it does not swell and become translucent, 

 as it does when treated with hydrochloric acid and pepsin. On the con- 

 trary, it becomes corroded on the surface, fragile, and in a short time under- 

 goes solution. The first product is a compound termed alkali-protein. 

 After solution has taken place, various chemic changes are initiated which 

 eventuate in the production of peptone and certain nitrogenized bodies, 

 leucin, tyrosin, aspartic acid, etc. The intermediate stages in this process 

 have not been satisfactorily determined. At no time during artificial 

 pancreatic digestion is there any evidence of the presence of the primary 

 proteoses. The secondary proteoses, however, are usually present. It 

 will be recalled that when the peptone of peptic digestion is subjected to the 

 action of trypsin a portion of it is decomposed into leucin and tyrosin, while 

 another portion presumably is not so decomposed, for which reason the 

 latter was called anti- and the former, hemi-peptone. It is now believed that 

 anti-peptone is not a peptone at all, but a compound termed carnic acid, 

 which can be decomposed into simpler nitrogen-holding bodies such as 

 leucin, tyrosin, arginin, etc. 



The action of trypsin on proteins in an alkaline medium may be illustrated 

 by the following scheme: 



Protein 



Alkali-protein 



Secondary proteoses 



When the proteins which have escaped digestion in the stomach pass 

 into the small intestine and mingle with the pancreatic juice, they are 



