DIGESTION 343 



while it is not important whether the gastric juice is poured 

 out a little sooner or a little later, and therefore it is left to 

 be called forth by the more tardy and haphazard method of 

 local action. Nevertheless, on looking a little closer, we 

 find that this does not exhaust the subject, and that the 

 gastric secretion can be influenced by events taking place ii\ 

 distant parts of the body, just as the salivary secretion can. 

 In a boy whose oesophagus was completely closed by a 

 cicatrix, the result of swallowing a strong alkali, and who 

 had to be fed by a gastric fistula, it was found that the 

 presence of food in the mouth, and even the sight or smell 

 of food, caused secretion of gastric juice (Richet). 



Here there must have been some nervous mechanism at work. 

 The secretion cannot have been excited by the direct action of 

 absorbed food products circulating in the blood an explanation 

 which has been given of the secretion seen in an isolated portion of 

 the cardiac end of the stomach during the digestion of food in the 

 rest. The efferent nervous channels through which these reflex 

 effects are produced have been defined by Pawlow's experiments on 

 dogs. He first made a gastric fistula, then a few days afterwards 

 divided the oesophagus through a wound in the neck, and stitched 

 the two cut ends to the edges of the wound. After the animals had 

 recovered, it was observed that when meat was given to them by the 

 mouth, a copious secretion of 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. Division of the splanchnic 

 nerves had no effect on this reflex secretion, while it could not be 

 obtained after division of both vagi. Further, stimulation of the peri- 

 pheral end of the vagus* caused secretion. These experiments 

 accordingly show that secretory fibres for the gastric glands run in 

 the vagi. But after division of the sympathetic fibres going to the 

 stomach, and also the vagi, gastric secretion is still caused by the intro- 

 duction of food into the stomach, so long as the vagi are cut below 

 the origin of their cardiac and pulmonary branches, and disturbance 

 of the heart and respiration thus avoided. And after section of both 

 vagi in dogs, no marked qualitative or quantitative changes have 

 been observed in the gastric juice. We must therefore suppose that 

 the gastric glands, while under the control of a reflex nervous 

 mechanism with its centre in the cerebrospinal axis, are also capable 

 of being locally stimulated through the peripheral ganglia in the 

 stomach walls, or directly by the mechanical contact of the food or the 

 contraction of the muscular fibres of the viscus, or the chemical 

 action of the products of digestion absorbed into the blood. 



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

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

 would have been stopped by the stimulation. 



