DIGESTION AND ABSORPTION IN THE STOMACH. 



to the exterior instead of entering the stomach. The animal thus had 

 the enjoyment of eating without actually filling the stomach. Eating 

 in this style forms what the author called a fictitious meal (Schein- 

 futterung). It was found that it causes ah abundant flow of gastric 

 juice as long as the vagi are intact, but has no effect on the secretion 

 when these nerves are cut. Evidently, therefore, the sensations of 

 taste, odor, etc., developed during the mastication and swallowing 

 of food set up reflexly a stimulation of secretory fibers in the vagus. 

 Pawlow designates a secretion produced in this way as a psychical 

 secretion, a term which implies that the reflex must be attended by 

 conscious sensations. In favorable cases the fictitious feeding has 

 been continued for five or six hours and a large amount of gastric 

 juice (700 c.c.) has been collected from a fistula, although no food 

 actually entered the stomach. It is important to note, also, that a 

 psychical secretion, once started, may continue for a long time after 

 the stimulus (the eating) has ceased. Experiments have been made 

 upon human beings under similar conditions. Thus, Hornborg* 

 reports the case of a boy with a stricture of the esophagus and a 

 fistula in the stomach. Food when chewed and swallowed did not 

 reach the stomach, but was regurgitated; it caused, nevertheless, 

 an active psychical secretion in the empty stomach. 



Normal Mechanism of the Secretion of the Gastric Juice. 

 During a meal the gastric juice is secreted, under normal conditions, 

 as long as the food remains in the stomach. The modern explana- 

 tion of the origin, maintenance, and regulation of this flow of secre- 

 tion is that given by Pawlow. Contrary to a former general belief, 

 he showed that mechanical stimulation of the gastric mucous mem- 

 brane has no effect on the secretion of the tubules. This factor may 

 therefore be eliminated. In an ordinary meal the secretion first 

 started is due to the sensations of eating that is, it is a psychical 

 secretion. The afferent stimuli originate in the mouth and nostrils; 

 the efferent path, the secretory fibers, is through the vagus nerve. 

 This reflex insures the beginning at least of gastric digestion, but its 

 effect is supplemented by reflex stimulations arising in the stomach 

 itself. The mucous membrane of the stomach contains sensory 

 fibers which, when stimulated, act reflexly upon the secretory fibers 

 and set up a secretion. It seems that some foods contain substances 

 capable of giving this effect, while others do' not. Thus, meat 

 extracts, meat juices, soups, etc., are particularly effective in this 

 respect; milk and water cause less secretion. Certain common 

 articles of food, such as bread and white of eggs, have no effect of this 

 kind at all. If introduced into the stomach of a dog through a fistula 

 so as not to arouse a psychical secretion, for instance, while the dog's 

 attention is diverted or while he is sleeping, they cause no flow of 



* Hornborg, " Skandinavisches Archiv f. Physiologie," 15, 209, 1904. 

 44 



