NERVOUS SYSTEM UPON SECRETION 175 



As has already been stated, the other functions of the vagus 

 are so important that the effects of the nerve 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 cesophageal 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 vagal 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 cesophageal 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 a process of sham feeding be now commenced, although the 

 dog takes and swallows the food greedily, no secretion of gastric 

 juice is evoked by the process, not a single drop flowing 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, 



