148 THE DIGESTIVE FLUIDS. 



ptyalin, and the lipolytic steapsin or pancreatic lipase. Chymosin 

 is further present in some animals, but absent in others. 



Like the ferments which are furnished by the salivary glands 

 and the central cells of the gastric glands, the enzymes of the pan- 

 creas occur in the pancreatic cells also in the form of zymogens, 

 which are subsequently transformed into the active ferments. If 

 a fresh pancreas is thus extracted with glycerin, it will be noted 

 that the resulting extract has no proteolytic properties whatever, 

 while an extract obtained after the gland has been hashed and ex- 

 posed to the air for some time, or an aqueous extract of the fresh 

 gland, digests albumins with ease. If the fresh gland, further, is 

 hashed and briefly treated with a 1 per cent, solution of acetic acid, 

 and then extracted with glycerin, an active preparation is obtained 

 at once. This transformation in the case of trypsin is effected by 

 the enterokinase of the duodenal mucosa, while steapsinogen is acti- 

 vated by the bile. The ptyalin also may exist in the gland cells 

 as a zymogen, but in the pancreatic juice it apparently only appears 

 as the free enzyme. When and how its activation takes place is 

 not known. 



The only case in which normal pancreatic juice has been obtained 

 from the human being is reported by Glassner. The total amount 

 of twenty-four hours varied between 700 and 900 c.c. ; the largest 

 secretion took place during digestion, and increased steadily until 

 the fourth or fifth hour, when a gradual decrease occurred. The 

 amount secreted while fasting represented from one-third to a half 

 of the total amount. The quantity was very materially influenced 

 by the ingestion of hydrochloric acid, increasing to twice the amount. 

 The secretion was absolutely devoid of any proteolytic properties, 

 but manifestly contained the preferment of trypsin, as it could be 

 readily activated by intestinal juice. Gltissner ascertained that in 

 the fasting condition the trypsinogen secretion is practically zero, 

 but that it slowly increases from the time when food is ingested, to 

 reach its maximum in the fourth or fifth hour, after which it again 

 decreases to the eighth hour. Parallel with the amount of trypsino- 

 gen runs the alkalinity curve. 



The fresh pancreatic juice has marked lipolytic properties, which 

 are increased by both the bile and the enteric juice, such that with 

 a mixture of the three secretions the activity is from four ^to five 

 times as great as in the case of the pancreatic juice alone. Like the 

 proteolytic power, so also does the lipolytic power of the pancreatic 

 juice reach its maximum in the fourth hour. In addition the pan- 

 creatic juice has marked diastatic properties, but it is incapable of 

 further decomposing the resulting maltose, which^ is effected by the 

 enteric juice. Neither a lactase nor an invertin is found in human 

 pancreatic juice. 



In chronic fistulse conditions are different, and the question 

 whether or not the digestive ferments will appear in the secretion 

 depends here upon the character of the stimulus given, viz., upon 

 the character of the food, With an exclusive meat diet trypsin 



