770 PHYSIOLOGY OF DIGESTION AND SECRETION. 



While the ultimate source of the chlorin of the hydrochloric acid 

 is to be found in the neutral chlorids of the blood (NaCl), certain 

 as yet unknown intermediate compounds are formed within the 

 parietal cells from which the acid is eventually produced. 



The Secretory Nerves of the Gastric Glands. — Although several 

 facts indicated to the older observers that the secretion of gastric 

 juice is under the control of nerve fibers, we owe the actual experi- 

 mental demonstration of this fact to Pawlow.* He demonstrated 

 +hat the secretion is under the control of the nervous system and that 

 the secretory fibers are contained in the vagus. Direct stimulation 

 of the peripheral end of the cut vagus causes a secretion of gastric 

 juice after a long latent period of several minutes. This long latencj 

 may^ be due possibly to the presence in the vagus of inhibitory 

 fibers to the gland, which, being stimulated simultaneously with the 

 secretory fibers, delay the action of the latter. Very striking proof 

 of the general fact that the secretion is due to the action of vagus 

 fibers is furnished by such experiments as these : Pawlow divided the 

 esophagus in the neck and brought the two ends to the skin so as to 

 make separate fistulous openings to the exterior. Under these con- 

 ditions, when the animal ate and swallowed food it was discharged 

 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 

 or sham meal {Scheinfiitterung) . It was found that it causes 

 an 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 desig- 

 nates 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-j- 

 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. 



* See Pawlow, "The Work of the Digestive Glands," translated by Thomp- 

 son, 1902. 



tHornborg, "Skandinavisches Archiv f . Physiologie," 15,209, 1904; see 

 also Bickel, "Verhandl. Kongr. f. innere Medizin," 23, 491, and Carlson, "The 

 Control of Hunger in Health and Disease," Chicago, 1916. 



