PHYSIOLOGY OF THE DIGESTIVE GLANDS 



441 



trie juice; cream takes considerably longer to be be digested than milk, 

 and the presence of oil in the stomach delays the secretion of juice poured 

 out on a subsequent meal of otherwise readily digestible food. By col- 

 lecting all of the gastric juice from the miniature stomach after feeding 

 by mouth with quantities of different protein-rich foods containing the 

 same quantities of nitrogen, interesting observations have been recorded 

 concerning the amount of juice secreted and its proteolytic power. The 

 results of some of the experiments are shown in the accompanying 

 curves (Figs. 150 and 151). 



It will be seen that the most abundant secretion occurs with meat, that 

 of milk being not only smaller but also slower in starting. The digestive 

 power is greatest in the case of bread. 



Hours 123456782345678923*56 



Flesh, 200 gm. 



Bread, 200 gm. 



Milk, 600 c.c. 



Fig. 151. Digestive power of the juice, as measured by the length of the protein column digested 

 in Mett's tubes, with diets of flesh, bread, and milk. (From Pavlov.) 



THE INTESTINAL SECRETIONS 



Pancreatic Juice 



Eegarding the natural secretion of pancreatic juice, little need be added 

 to what has already been said (see page 425) . The secretion begins when the 

 chyme enters the duodenum, and attains its maximum when the outflow 

 of this is greatest. By collecting the juice from, a permanent fistula of the 

 pancreatic duct, it has been found that the amount varies with different 

 foods. When quantities of food containing equivalent amounts of nitro- 

 gen are fed, the greatest secretion is said to occur with bread and the least 

 with milk. Such differences are probably dependent upon the amount of 

 acid secreted in the stomach and passed on into the duodenum. It was 

 thought at one time that, besides variation in quantity, the nature of the 

 enzymes in the pancreatic juice might vary according to the kind of 

 food. This, however, has been shown not to be the case. 



