108 PHYSIOLOGY CHAP. 



The nerves to the stomach consist of the terminal gastric 

 branches of the vagus, and the sympathetic fibres of the solar 

 plexus. Both are almost invariably composed of non-medullated 

 fibres. Numerous small ganglia (according to Eemak) form 

 plexuses with these nerve fibres, either between the layers of the 

 muscular coat or in the submucosa. From these plexuses, nerve 

 fibres run through the muscular tissue, or the glandular tissue of 

 the mucous membrane. 



XII. Until recently the direct influence of the nervous system 

 on gastric secretion was regarded as doubtful. The results of 

 experiments were either negative or less obvious than for the 

 salivary secretion. Kecent experiments have fully elucidated this 

 point. 



The flushing of the gastric mucosa owing to active vascular 

 dilatation during digestion, the increased rate of circulation which 

 causes bright red blood to flow through the veins that differs 

 little from that in the arteries (Claude Bernard), are phenomena 

 perfectly analogous to those observed during salivary secretion. 

 They show the existence of vasomotor nerves to the stomach, and 

 justify the conjecture that special secretory nerves control the 

 gastric, like the salivary, secretion. 



A stronger argument for the direct nervous control of gastric 

 secretion lies in the fact that in fasting animals with a gastric 

 fistula, the mere sight or smell of some favourite food causes a 

 flow of gastric juice through the fistula (Bidder and Schmidt, 

 1842 ; Schiff, 1865). This is not due to deglutition of saliva, 

 which might excite the gastric mucous membrane, because the 

 same thing is seen when the ducts of the salivary glands or the 

 oesophagus are occluded in the dog. The secretion "psychically 

 excited " by sight or smell does not begin immediately, but only 

 after some (5-15) minutes, and persists for a long time after 

 cessation of the stimulus (Sanotzky, 1892). 



Greater interest attaches to Bichet's observations (1878) on a 

 girl who had stricture of the oesophagus and was fed through a 

 gastric fistula. Each time she was made to chew or taste a highly 

 sapid substance (sugar, lemon juice, etc.) while fasting, a con- 

 siderable quantity of juice flowed from the fistula. This was 

 undoubtedly a reflex secretion, but it was uncertain whether the 

 reflex directly promoted the secretion, or if, by dilating the vessels 

 of the stomach, and contracting its muscular coat, it determined 

 the secretory phenomenon indirectly. 



Pawlow and Mme. Schumovva-Simanowskaia (1889) made a 

 series of striking experiments in order to decide this question and 

 clear up these phenomena of the innervation of the gastric glands. 

 They established the usual gastric fistula on dogs, and in a 

 subsequent operation divided the oesophagus half-way up the neck, 

 and sutured the two ends to the lips of the cutaneous wound, so 



