280 INFLUENCE OF THE 



are so important that the effects upon gastric secretion cannot be 

 observed by the usual simple methods of section and of stimulation 

 of the nerve, without certain preliminary operations which allow 

 of section and stimulation without calling forth an interference at 

 the same time with other important functions. The procedures 

 differ somewhat according to whether the effects of section or of 

 stimulation of the vagus are to be tested, and hence it is better to 

 describe each experiment separately. 



Effects upon Gastric Secretion of Section of the Vagal Fibres. 

 The operation is carried out upon a dog in two stages. In the first 

 stage an ordinary permanent gastric fistula fitted with a metallic 

 cannula is made, and in addition an ossophageal fistula, so that 

 the mouth is cut off from all communication with the cavity of 

 the stomach. At the same operation the right vagus nerve is 

 divided below the point of exit of the recurrent laryngeal and 

 cardiac branches, so that on any subsequent section at a later 

 stage of the left vagus the control of the larynx and heart will still 

 be left in action. If at some time after recovery from the operation 

 food is offered to the animal and is eaten, it of course drops out by 

 the oesophageal fistula and nothing reaches the stomach. Under 

 such circumstances, however, and although the gastric fibres of 

 the vagus on the right side have been completely severed, a copious 

 flow of gastric juice is obtained which starts about five minutes 

 after the commencement of the sham feeding. If now the left 

 vagus be dissected out and severed there is no profound general 

 disturbance of functions, because, although the pulmonary and 

 abdominal vagal fibres on both sides are paralysed, the laryngeal 

 and cardiac fibres on the right side are still intact. If now a 

 process of sham feeding be commenced, although the dog takes and 

 swallows the food greedily, no secretion of gastric juice is evoked 

 by the process : not a single drop flows from the gastric fistula. 



In the same animal in which the above procedures had been 

 carried out the right vagus was at a later period divided in the 

 neck, yet the animal continued in perfect health and enjoyed its life 

 to the full, although both cervical vagi were now severed. Double- 

 cervical vagotomy was also carried out in similar fashion upon a 

 second dog, which survived the double operation for months. In both 

 these animals, after the severance of the second vagus, sham feeding 

 was found never to give rise to a secretion, although often tested. 



In addition to demonstrating that the vagus is at any rate the 



