282 INFLUENCE OF THE 



peripheral vagus immediately after section. The experimental pro- 

 cedure was to perform tracheotomy, so that artificial respiration 

 could be carried on, to cut the spinal cord beneath the medulla so 

 as to throw out reflex action upon the gastric glands, to sever the 

 vagi, keeping the peripheral ends attached to ligatures for stimula- 

 tion, to establish an ordinary gastric fistula, and to ligature off 

 the stomach from the oesophagus and pylorus. The results of 

 stimulation of the vagus in these acute experiments were not, 

 however, invariably the same ; in more than half of the experiments 

 a flow of secretion was obtained, but the latent period was prolonged 

 from the usual five minutes to from fifteen minutes to an hour or 

 more, and the causal connection of a secretion occurring an hour 

 after stimulation has commenced is, to say the least of it, very 

 doubtful. After the nerve had once commenced to work, however, 

 the dependence of the secretion upon the stimulus became more 

 apparent, for on removal of the stimulus the process of secretion 

 gradually stopped, and on renewal of the stimulus, secretion now 

 appeared with greater rapidity. Administration of atropin stopped 

 the secretion. Pawlow explains the long latent period on the 

 assumption that the vagus contains inhibitory fibres as well as 

 excitatory fibres for the gastric glands. 



Nothing is known worth recording regarding the action upon 

 the secretion of the sympathetic fibres which run to the stomach. 

 It is almost impossible to find and stimulate these after they leave 

 the solar plexus. It has been stated that gastric secretion still 

 persists after section of the splanchnics ; but this fact alone proves 

 nothing as to the possible effect of these nerves in initiating, 

 inhibiting, or controlling gastric secretion. 



Innervation of the Pancreas. The study of the influence of its 

 nerve-supply upon the secretory activity of the pancreas has proved 

 one of the most difficult and perplexing of the problems of gland 

 innervation, and we cannot yet be said to be in possession of clear 

 and complete information as to the influence of its nerves upon 

 the physiological activity of this most important gland. But 

 the study of the subject has indirectly led to most important results 

 in the discovery of the fact that gland activity may be called out, 

 apart from nervous activity, by the chemical action directly upon 

 the gland cells of substances which are formed in cells in other 

 regions away from the gland, and are carried by the blood-stream 

 directly to the gland cells. 



