264 DIGESTION 



gus does not of itself produce any gastric secretion, yet when the animal has 

 some desire for food this excitation intensifies considerably the psychical secre- 

 tion which would otherwise take place, and raises both the acidity and the 

 digestive power of the secretion. 



In the case of a five-year-old boy with a complete oesophageal stricture and 

 a gastric fistula, Hornborg found that chewing 1 palatable foods induced, after 

 an average latent period of seven minutes, a secretion which lasted for forty 

 minutes or more, whereas chewing disagreeable foods, or chemically active 

 (lemons) or indifferent substances (rubber) was without any influence on the 

 gastric glands. It is worthy of note that the secretion failed when the boy was 

 not permitted to eat immediately food particularly palatable to him, and began 

 to cry; also that every time he was fed through the stomach fistula he wished 

 for something edible to chew. Mere sight of food was not effective in provoking 

 the secretion. 



(2) The Secretion Independent of the Vagus. Mechanical stimulation of the 

 stomach mu'cosa, even when it is very energetic, causes no secretion of gastric 

 juice whatever; only an alkaline mucus flows from the fistula (Pawlow). The 

 secretion not mediated by the vagus must be the result, therefore, of chemical 

 stimulation. In order to study this question more closely and to prevent mixture 

 with foreign substances, Heidenhain separated the fundus portion from the rest 

 of the stomach by a surgical operation, and thus prepared an isolated " fundus 

 fistula." In this operation the branches of the vagus which mediate the secretory 

 reflex were cut. Nevertheless, when the animal received something to eat secre- 

 tion appeared in the blind sac. It began fifteen to thirty minutes after eating 

 and continued for a longer or shorter time according to the quality and quantity 

 of the food after a moderately full meal, thirteen to fourteen hours; after a 

 very full one, sixteen to twenty hours. When the dog was given very slightly 

 digestible food, such as coarsely chopped ligamentum nuchaB, no secretion ap- 

 peared, but began when he was subsequently allowed to drink. Even then the 

 secretion continued for only a short time, one and one-half to four hours at most. 



Pawlow and Chigin carried out even more detailed experiments on dogs in 

 which the blind sac was prepared without section of the vagus branches. The 

 substances whose effects on the mucous membrane were to be tested were intro- 

 duced (without the dog's knowledge) through a fistula directly into the main 

 part of the stomach. Water, 0.1-0.5-per-cent HC1 solutions, etc., in quantities 

 of 100-150 c.c. exerted only a very slight influence on the process of secretion in 

 the isolated sac. In quantities of 500 c.c. pure water, ten-per-cent solutions of 

 cane sugar or starch, or egg albumin provoked a somewhat stronger secretion. 

 This began in a majority of cases after thirteen to twenty-nine minutes. Since 

 distilled water evoked just as much secretion as the solutions, it is assumed that 

 the effects here are only those of the solvent. Weak soda solutions reduced the 

 effect of water. Fats also exerted an inhibitory influence. 



When meat gravy, meat juice and meat extract or milk, or a solution of 

 gelatin in water were introduced into the stomach in the same way, results were 

 very different. An abundant secretion began after an average latent period of 

 thirteen minutes, which continued for about three hours. Neither egg albumin 

 nor albumose nor bread had any such effect. It appears therefore that certain 

 extractives contained in meat, to which however creatin and creatinin do not 

 belong, certain constituents of milk, etc., are specific stimuli for the stomach. 

 Furthermore, there are experiments which show that once the secretion is started 

 by these substances, it is considerably augmented when, for example, egg albu- 

 min, of itself but slightly active, is introduced. In the same way starch intro- 

 duced with meat can intensify the secretory process considerably. 



