INTERNAL SECRETION OF PANCREAS 35 



quantity of juice and digestive strength are considered to- 

 gether a bread diet causes a secretion of greater proteolytic 

 power than milk or meat. But there is no more evidence 

 that the adaptation of the pancreatic juice to the nature of 

 the food is due to a specific sensibility of the duodenal mucosa 

 to the various foodstuffs than in the case of the gastric juice. 

 For the volume of the chyme and its acidity determine the 

 amount of secretin formed, and, therefore, the intensity of 

 pancreatic secretion. 



It has been discovered that the pancreatic juice obtained 

 from a fistula may have little or no digestive action on proteins 

 unless brought in contact with the duodenal mucosa. The 

 trypsin is secreted in a zymogen form and requires to be acti- 

 vated by a substance furnished by the mucosa. This substance 

 is supposed to be an enzyme, and is known as enterokinase. 

 Its action is not specific, since the salts of calcium and magne- 

 sium can activate trypsinogen. This relation possibly serves 

 to protect the ducts of the pancreas from digestion. 



Internal Secretion of Pancreas. The pancreas is indispensable 

 to life, especially in carnivora. Loss of the external secretion 

 affects fat digestion, but does not necessarily shorten life. 

 Extirpation of the pancreas, however, in dogs within twenty- 

 four hours leads to profound disturbances in metabolism, 

 showing itself mainly by the presence of sugar in the blood 

 and urine, by polyuria, polydipsia, polyphagia, and emacia- 

 tion. Dogs may live two or three weeks. Resistance to bacterial 

 invasion is lessened, so that extensive suppuration of the wound 

 often results. When carbohydrates are excluded from the 

 diet, or no food whatsoever is given, sugar still continues to 

 be formed. Protein destruction is increased. When one- 

 fourth to one-fifth of the pancreas is left, even when trans- 

 planted (with intact circulation) to other portions of the body, 

 the symptoms are absent. In some manner the pancreas 

 influences metabolism. Since injection of the blood of depan- 

 creatized animals into normal animals gives no serious effects, 

 it cannot be that the symptoms of pancreas extirpation are 

 due to the accumulation of toxic bodies within the blood. 

 It is better to assume that the pancreas furnishes the body 

 with something necessary to the regulation of its sugar, 

 either in its storage, or its conversion from glycogen, or its 

 combustion by the tissues. 



