Effects of Vagus Stimulation on Dog's Stomach. 229 



Results. 



Effect of Repeated Vagus Stimulation. — In the dog stimulations 

 of the vagus with a tetanizing current repeated at short intervals 

 with a given strength of current are followed by contractions of 

 the stomach of approximately uniform amplitude. Complete 

 cardiac inhibition was observed during each stimulation. The 

 apparent ability to produce an artificial rhythm of the dog's 

 stomach by repeated stimulations of the vagus is in striking con- 

 trast to the rapid failure of gastric contractions on repeated vagus 

 stimulation in the turtle. 



Effect of Prolonged Vagtis Stimulation. — Prolonged stimulation 

 of the vagus with a tetanizing current of moderate strength and 

 also a strong tetanizing current is followed by only a single con- 

 traction of the stomach and its usual subsequent relaxation in 

 spite of continued stimulation. Weak peristalses in the pyloric 

 region may occur after the one contraction during the balance of 

 the stimulation but usually stops shortly after the stimulation has 

 ceased. There is no indication of a tetanus or increased tone of 

 the stomach. These results are similar to those obtained in the 

 turtle. 



It was noted from the blood-pressure tracings and also from 

 direct observation of the heart that complete vagus inhibition of 

 the heart failed at about the same time as the relaxation of the 

 stomach began. It would seem that the mechanism operating 

 to prevent gastric tetany is the same as that which prevents 

 prolonged complete cardiac inhibition from vagus stimulation. 



Influence of Cooling. — In dogs cooled to 25 0 C. to 23 0 C. it 

 was found that repeated stimulations of the vagus were followed 

 by no indications of either failure of gastric response or increased 

 or permanent tone as the result of the stimulations. Prolonged 

 vagus stimulation at this temperature is not followed by tetanus 

 of the stomach. 



It was further noted that at a temperature of 21 0 C. there was 

 a failure to obtain a gastric response from vagus stimulation but 

 stimulation of the stomach wall was followed by a contraction. 

 No cardiac inhibition was noted at this temperature in response to 

 vagus stimulation. As the temperature was raised there was a 

 corresponding increase in gastric response to stimulation of the 

 vagus. 



