NERVOUS SYSTEM UPON SECRETION 177 



of the vagus in gastric secretion by this so-called " chronic " 

 method, Pawlow and his co-workers returned to the attempt to 

 obtain evidence by the so-called " acute " method of stimulation 

 of the peripheral vagus immediately after section. The experi- 

 mental procedure 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 stimulation, 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 in- 

 hibitory 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 

 che 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, 



M 



