PANCREATIC JUICE. 235 



from whom a tumor of the pancreas had been removed. The 

 analysis of this was as follows : 



Water 864.05 



Proteids 92.05 



Other organic substances 40.46 



Salts 3.44 



Enzymes of Pancreatic Juice. It is a remarkable fact that the 

 pancreatic juice of all vertebrates, so far as examined, contains 

 four enzymes : (1) amylolytic, (2) proteolytic, (3) fat-splitting, and 

 (4) milk-curdling. 



Amylopsin. This is the amylolytic enzyme of the pancreatic 

 juice, and is regarded as identical with ptyalin of the saliva, 

 although pancreatic juice has much greater amylolytic power than 

 saliva, and acts upon uncooked starch ; but whether this is due to 

 a difference in the enzymes or because in pancreatic juice the 

 enzyme is more concentrated, has not been determined. Some 

 authorities include them both under the name of ptyalin. 



Amylopsin appears in the pancreatic juice for the first time 

 about one month after birth, while ptyalin is present in the human 

 parotid gland at birth, but in the submaxillary gland not until 

 about two months subsequently. 



The optimum temperature for amylopsin is from 30 C. to 

 45 C., while between 60 C. and 70 C. it is destroyed. Its 

 activity is greatest when the reaction is neutral or when a minute 

 trace of acid is present, such as, for instance, 0.01 per cent, of 

 hydrochloric acid. Its action on starch is to change it to maltose 

 -and dextrose, or, under some circumstances, to maltose alone. 

 Authorities who regard the action of saliva upon starch as being 

 of comparatively little importance look to amylopsin and to the 

 amylolytic enzyme of the intestinal juice as the principal agents 

 in starch conversion. This we regard as a mistake, and are in- 

 clined to place a much higher value upon salivary digestion than 

 do these, but at the same time would give pre-eminence to the 

 pancreatic juice as a starch converter. 



Trypsin. This is the proteolytic enzyme of the pancreatic juice, 

 and its power in this regard is greater than that of pepsin. It 

 has been found in the pancreatic juice during the last third of fetal 

 life. Its activity is greatest when sodium carbonate is present to 

 the amount of about 1 per cent., although it acts when the reac- 

 tion is neutral or very slightly acid. When hydrochloric acid 

 is present to any considerable extent the enzyme is destroyed, and 

 this is hastened when pepsin is also present. 



Trypsin has never been isolated, so that its chemical com- 

 position has not as yet been determined. In the action of the 

 cells of the pancreas, the zymogen trypsinogen is first formed, 

 and this later becomes trypsin. In studying its action, a pancreas 



