204 PHYSIOLOGY OF ALIMENTATION. 



by the following facts. The food upon entering the mouth is 

 able to stimulate the buccal mucous membrane, either chem- 

 ically, mechanically, or in both of these ways. Application 

 of such substances as acids, salts, bitters, pepper, mustard, 

 etc., to the mucous membrane of an oesophagotomized dog 

 never calls forth a secretion of gastric juice, however. Not 

 even does a meat decoction in most instances prove effective 

 in this regard. Nor does a combination of mechanical stimu- 

 lation with the chemical, such as wiping out the mouth with 

 an acid-soaked sponge, or giving the dog stones to swallow, 

 work any more successfully in exciting the gastric mucous 

 membrane. The stones drop out of the oesophagus, and, 

 even if this play is kept up for hours, not a drop of gastric 

 juice flows from the gastric fistula. As soon, however, as 

 the old experiment of sham feeding is tried, and meat or bread 

 is given the dog instead of stones, a free flow of gastric juice 

 begins in five minutes and steadily increases in amount as 

 " described above. These facts prove clearly that the nerves 

 of the stomach are not excited reflexly through chemical or 

 mechanical stimulation of the buccal mucous membrane. 

 Wherein 1 * then does he sham feeding with food differ from 

 that with stones? In the former case the dqg eagerly de- 

 sires its meal, something which is lacking in the latter. This 

 ' eager desire for food, the appetite in other words, is the excitant 

 of the gastric flow, and we must conclude in consequence that 

 a psychic state rather than a reflex from the mouth acts as 

 the normal excitant of the vagus nerve and the gastric mucosa 

 at the beginning of a meal. 



BIDDER and SCHMIDT observed years ago that merely offer- 

 ing a hungry dog food excited a flow of gastric juice. PAW- 

 LOW has confirmed and elaborated this experimental finding. 

 Actual sham feeding with foqd does not need to be indulged 

 in in order to obtain a flow of gastric juice. If only a tempting 

 meal be prepared before a hungry dog, a flow of gastric juice, 

 such as has been described when sham feeding is practised, 

 begins within five minutes after the teasing is begun. In 



