SECRETION. 181 



through the sensory nerves of the mouth, and probably also by psychical 

 states. 



Normal Mechanism of Secretion of the Gastric Juice. Our know- 

 ledge of the means by which the flow of gastric secretion is paused during 

 normal digestion, and of the varying conditions which influence the flow, is 

 as yet quite incomplete. Some notable experiments recently made by Pawlow l 

 and Khigine, together with older experiments by Heidenhain, 2 have, however, 

 thrown some light upon this difficult problem, and have, moreover, opened 

 the way for further experimental study of the matter. Heidenhain cut out 

 a part of the fundus of the stomach, converted it into a blind sac, and brought 

 one end of the sac to the abdominal wall so as to form a fistulous opening to 

 the exterior. The continuity of the stomach was established by suturing the 

 cut ends, but the fundic sac was completely separated from the rest of the 

 alimentary canal. He found that under these conditions the ingestion of 

 ordinary food caused a secretion in the isolated and empty fundic sac, the 

 secretion beginning fifteen to thirty minutes after the food was taken, and 

 continuing until the stomach was empty. The ingestion of water caused a 

 temporary secretion in the fundus, while indigestible material such as liga- 

 mentum nuchae gave no secretion at all. Heidenhain's interpretation of these 

 experiments as applied to normal secretion was that in ordinary digestion we 

 must distinguish between a primary and a secondary secretion. The pri- 

 mary secretion depends upon the mechanical stimulus of the ingested food, 

 and is confined to the spots directly stimulated ; the secondary secretion begins 

 after absorption from the stomach is in progress, and involves the whole 

 secreting surface. In the experiments related above, the secretion from the 

 isolated fundus was a part of this secondary secretion. The stimulus in this 

 case would seem to be a chemical one, consisting of some of the products 

 absorbed from the stomach, which either acts directly on the gastric glands 

 or indirectly on the intrinsic nerve-centres of the stomach. 



Khigiue has made similar experiments, but altered the operation so that the 

 isolated fundic sac retained its normal nerve-supply, which in Heidenhain's 

 operations was apparently injured. The results which he obtained are much 

 more complete than any hitherto reported. He was able in the first place to 

 determine the eifect of various diets upon the amount of gastric secretion, upon 

 its acidity, and upon its digestive power, using the secretion from the isolated 

 fundic sac as typical of what was going on in the rest of the stomach in which 

 the food was actually in process of digestion. One of his curves showing the 

 effect of a mixed diet (milk, 600 cubic centimeters ; meat, 100 grams ; bread, 100 

 grams) is reproduced in Figure 80. It will be seen that the secretion began 

 shortly after the ingestion of food (seven minutes) and increased rapidly to a 

 maximum which it reached in two hours. After the second hour the flow 

 decreased rapidly and nearly uniformly to about the tenth hour. The acidity 

 also rose slightly between the first and second hours, and then fell gradually. 



1 Khigine : Archives des Sciences biologiques, St. Petersburg, 1895, vol. iii. p. 461. 



2 Hermann's Uandbuch der Physiologic, 1883, Bd. v. S. 114. 



