434 DIGESTION 



movements of the viscus, but also concerning the rate of discharge of 

 food into the intestine and therefore the duration of the gastric digestive 

 process. Carlson's contribution has been rendered possible by his good 

 fortune in having in his service a second Alexis St. Martin, a man with 

 complete closure of the esophagus and a gastric fistula large enough to 

 permit of direct inspection of the interior of the stomach. Seizing the 

 opportunity thus presented, Carlson during the last four or five years 

 has devoted his attention exclusively to a thorough investigation, not 

 only of the movements of the stomach, but also of the rate of secretion 

 of the gastric juice under different conditions. He has also, with praise- 

 worthy enthusiasm and keen scientific spirit, extended his observations 

 both on laboratory animals and on himself and his coworkers, so as not 



Fig. 148. Diagram of stomach showing miniature stomach (5) separated from the main stomach 

 (V) by a double layer of mucous membrane. A. A., is the opening of the pouch on the abdominal 

 wall. (Pavlov.) 



to incur the error, which is all too frequently made, of confining the 

 observations to one species of animal. 



The Nervous Element in Gastric Secretion 



The first stimulus to the secretion of gastric juice is nervous in origin, 

 and is dependent on the gratification of the appetite and the pleasure of 

 taking food. This fact, after having been suggested by observations 

 made in the clinic, was first thoroughly investigated by Pavlov, who for 

 this purpose observed the gastric secretion flowing either from a fistula 

 of the stomach itself, or from a "miniature stomach," in dogs in which 

 also an esophageal fistula had been established. When food was given 

 by mouth to these animals, it was chewed and swallowed in the usual 

 manner, but before reaching the stomach, it escaped through the esopha- 



