202 PHYSIOLOGY OF ALIMENTATION. 



When sham feeding no longer produces a secretion of gastric 

 juice after double vagotomy, it does not mean, however, that 

 the gastric glands have lost the power of secretion. As will 

 be shown later, highly active juice can, under appropriate 

 circumstances, still be obtained from this digestive organ. 

 The above experiment only shows that certain exciting in- 

 fluences which normally, in the ordinary process of eating, 

 reach the gastric mucosa by way of the vagi have been 

 removed. As has been shown by KETSCHER, the mode of 

 feeding and the character of the food presented to the dog 

 during sham feeding alters markedly the character of the 

 gastric juice obtained. If the dog is given pieces of meat at 

 long intervals, less gastric juice and one lower in digestive 

 power is obtained than when the dog is fed more rapidly^- 

 In a similar manner, a diet of meat, which the dog relishes 

 highly, produces more juice and one having a higher digestive 

 power than a meal of bread, which the dog relishes less. 



The existence of nerve fibres in the vagus which influence 

 the secretion of gastric juice was proven above by showing 

 that after division of both vagi stimulation of the buccal 

 cavity with food no longer excited the gastric mucosa to 

 activity as before. It can, however, be shown by direct 

 stimulation of the vagus in a properly performed experiment, 

 that this nerve contains fibres which influence the activity 

 of the stomach. This has been accomplished by PAWLOW and 

 ScHUMOW-SiMANOWSKi. A gastrotomized and cesophagot- 

 omized dog, in which the right vagus nerve has been cut below 

 the origin of the inferior laryngeal and cardiac fibres, is used 

 for the experiment. Three or four days before stimulation 

 of the vagus is to be carried out, the left vagus is carefully 

 dissected out in the neck, a ligature passed around it but not 

 tied, and the whole carefully preserved under the skin. On 

 the day the vagus stimulation is to be carried out, the wound 

 is painlessly opened and the nerve laid bare. By attending 

 to these details, whereby appreciable pain to the animal is 

 avoided, excitation of the vagus by induction shocks at in- 



