32 SECRETION 



a small artificial stomach formed by resecting a protion of the 

 stomach wall gives a means of testing the characteristics of 

 the secretion. Numerous trials have indicated that the secre- 

 tion of such a small stomach is identical in its properties with 

 the secretion in the main portion of the stomach. 



The smell, taste, or sight of food by a dog thus operated 

 upon leads in five or six minutes to the appearance of a copious, 

 secretion. If, furthermore, the esophagus be sectioned in 

 the neck and the cut ends brought to the skin on the neck, 

 a dog may be fed for an indefinite time leading to continued 

 secretion. This "sham" feeding is ineffective if the vagi are 

 cut. In the case of the stomach glands there exists, therefore, a 

 psychical secretion just as in the case of the salivary glands. 

 This has been observed in a human being in which there was 

 an occlusion of the esophagus. It must not be imagined that 

 in sham feeding it is the stimulation of the buccal nerves that 

 reflexly leads to the secretion of the gastric juice. A strong 

 chemical stimulus like dilute acid applied to the mucous mem- 

 brane of the mouth does not cause a gastric secretion, although 

 the salivary flow is profuse. It is the appetite that determines 

 the flow of the gastric juice. 



When foods are introduced into the stomachs of sleeping 

 dogs through fistulous openings the effect upon secretion 

 varies with the kind of food. Bread and the white of egg 

 are entirely ineffective during the first hour or so. Raw flesh 

 is more effective, causing a secretion in fifteen to forty-five 

 minutes. Section of the vagi or destruction of the abdominal 

 sympathetic plexus does not abolish the result, especially, 

 after water or meat extract. This difference in results with 

 different foods has given rise to the conception of definite 

 chemical excitants or secretogogues which stimulate the gastric 

 gland cells after absorption. Raw flesh contains them pre- 

 formed. They are formed in bread and in the white of egg 

 by the action of the psychical secretion. However, food sub- 

 stances (broth, dextrin), containing secretogogues do not 

 stimulate the gastric glands when injected into the blood 

 directly, but must first act on the gastric mucous membrane. 

 The secretogogues are regarded as giving rise to a new sub- 

 stance by their action on the gastric mucosa a substance 

 known as gastrin, representative of that class of substances 



