472 DIGESTION 



lowed by thorough digestion and assimilation than occasional stuffing 

 with larger amounts. We see too in these experiments an explanation 

 of the well-established practice of starting a meal with something 

 savory. A hors d'oeuvre is nothing more than a physiological stimulant 

 to appetite. It is also interesting from a practical standpoint to observe 

 that with those who have a keen relish for sweetmeats the taking of des- 

 sert has a real physiological significance, for, as in Carlson's patient, it 

 stimulates toward the end of a meal a further secretion of the gastric 

 juice, and thus insures a more rapid digestion of the food. Good cooking, 

 it should be remembered, is really the first stage in digestion, and it is 

 the only stage over which we can exercise voluntary control. 



The Hormone Element in Gastric Secretion 



Although gastric digestion is initiated by the appetite juice, it is 

 clear that this alone can not account for all the secretion that occurs 

 during the time the food is in the stomach. After an ordinary meal this 

 occupies usually about four hours, whereas we have seen, particularly 

 from Carlson's observations, that the appetite juice lasts only for some 

 fifteen or twenty minutes after the exciting stimulus has been removed. 

 The appetite juice, in other words, serves only to initiate the process of 

 secretion, and the question arises, What keeps up the secretion during 

 the rest of gastric digestion? The answer was furnished by Pavlov, who 

 observed animals in which not only a miniature stomach had been made, 

 but a fistula into the main stomach as well. The behavior of the secre- 

 tion of gastric juice as a whole could be followed by collecting that 

 which was secreted in the miniature stomach, for it was shown, in con- 

 trol experiments, that this secretion runs strictly parallel with that in 

 the main stomach, being quantitatively a definite fraction of it accord- 

 ing to the relative size of the miniature stomach and qualitatively 

 identical. The miniature stomach, in other words, mirrors the events 

 of secretion in the main stomach. 



It was observed that when the animal was allowed to take the food 

 into the main stomach by the mouth and esophagus, the secretion from 

 the miniature stomach continued to flow until the process of gastric 

 digestion had been completed, a result which was quite different from 

 that obtained after sham feeding. The only possible explanation for this 

 result is that the food in the stomach sets up secretion as a result of 

 local stimulation. To investigate the nature of this local stimulation, 

 whether mechanical or chemical, food and other substances were placed 

 in the main stomach through the gastric fistula without the animal's 

 knowledge so as to avoid possible psychic stimulation, and the secretion 

 observed from the miniature stomach. When the mucous membrane of 



