402 



DIGESTION 



Py/oru. 



Plexus gast 

 anterior 



gastric juice followed in five or six minutes, notwithstanding the 

 fact that in this ' sham feeding ' the food immediately escaped from 

 the opening in the upper portion of the divided oesophagus. Much 

 the same result was seen when the food was simply shown to the 

 animal. Indeed, when a hungry animal is tempted with the sight 

 of meat, the flow of gastric juice, always occurring after a latent 

 period of five or six minutes, may be even greater than with sham 

 feeding. Division of the splanchnic nerves had no effect on this 

 reflex secretion, while it could not be obtained after division of both 

 vagi below the origin of their cardiac and pulmonary branches, by 

 which disturbance of the heart and respiration are avoided. 

 Further, stimulation of the peripheral end of the vagus in the neck* 

 caused secretion. These experiments show that secretory fibres 

 for the gastric glands run in the vagi. It is probable that the vagi 



also contain 

 efferent fibres 

 which inhibit 



ophagus , 



the gastric 



Plexus gastn'eus T,, ' 



posterior vagi, secretion. 1 ne 

 excitation of 

 the secretory 

 fibres is not 

 produced re- 

 flexly by the 

 processes of 

 mastication 

 and deglutition 

 as such. Di- 

 lute acid is the 

 most powerful 

 chemical stim- 

 ulus for the 

 buccal mucous 

 membrane, and 



when it is introduced into the mouth of a dog with a double 

 cesophageal and gastric fistula, an abundant secretion of saliva at 

 once ensues. But no matter how long the animal continues to 

 swallow the mixture of saliva and acid, no gastric juice is formed. 

 The same is the case in sham feeding with salt, pepper, mustard, 

 smooth stones, and even extract of meat. It is the desire for food 

 the appetite, as we call it and the feeling of satisfaction associa- 

 ated with eating food that the animal relishes, which is the efficient 

 cause of the gastric secretion in sham feeding. The more eagerly 

 the dog eats, the greater is the flow of gastric juice. 



* The nerve was not stimulated till a few days after the section, so as to 

 allow the cardio-inhibitory fibres to degenerate. Otherwise the heart would 

 have been stopped by the stimulation. 



Fig. 161. Pawlow's Stomach Pouch. AB, line of incision; 

 C, flap for forming the stomach pouch. At the base of 'the 

 flap the serous and muscular coats are preserved, and only 

 the mucous membrane divided, so that the branches of the 

 vagus going to the pouch are not severed. 



