THE REGULATION OF GASTRIC SECRETION. 209 



when the food is introduced into the stomach directly, but 

 also by the fact that the effect of sham feeding does not last 

 as long as an ordinary digestive period nor yield in the later 

 hours of this period as active a juice as is obtained after a 

 true meal. What, then, are the other excitants of the gastric 

 flow besides the appetite which we have seen above plays so 

 important a role in digestion? We think naturally of the 

 mechanical stimulation and secondly of the chemical stimu- 

 lation which might be brought about by the presence of the 

 food in the stomach. Let us first see if mechanical stimu- 

 lation is effective in bringing about a secretion of gastric 

 juice from the stomach. 



Almost without exception the older observers believed that 

 mechanical stimulation of the gastric mucosa by a feather 

 or a glass rod would yield at least some secretion of gastric 

 juice. Within recent years, however, this question has been 

 investigated by PAWLOW and his cow^rkers, who have pointed 

 out the sources of error in the older experiments, and today 

 we say that mechanical stimulation is ineffective in bringing 

 about a secretion of gastric juice. This is shown by the follow- 

 ing experiment. 1 



In an oesophagotomized dog possessing a gastric fistula 

 the stomach is first thoroughly washed out with water. If 

 the mucous membrane is now mechanically stimulated by 

 moving a feather or a glass rod over it continuously for a 

 half hour or more, or if a stream of fine sand is blown against 

 it, or finally, if the stomach is distended to the size of a child's 

 head by inserting within it a rubber ball, not a single drop of 

 gastric juice is discharged. Only a little mucus which turns 

 red litmus paper blue may be expelled. But let sham feed- 

 ing with bread or meat be carried out upon the same dog, and 

 an acid juice appears within five or ten minutes after the 

 beginning of the feeding. The older observers never obtained 



1 PAWLOW : Work of the Digestive Glands. Translated by THOMP- 

 SON, London, 1902, p. 86. 



