PHYSIOLOGY OF THE DIGESTIVE GLANDS 



437 



of diet and the feeding of patients during convalescence, is obviously 

 very great. However perfect in other regards a diet may be, it will 

 probably fail to be digested at the proper rate unless it is taken with 

 relish. Frequent feeding with favorite morsels is more likely to be fol- 

 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 physiologic 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 physiologic significance, for, as in Carlson's patient, it 

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



25' 



SO' 



Chewing food 



Fig. 149. Typical curve of secretion of gastric juice collected at 5-minute intervals on mas- 

 tication of palatable food for 20 minutes. The rise in secretion during the last 5 minutes of 

 mastication is due to chewing the dessert (fruit) for which the person had great relish. (From 

 Carlson.) 



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 normal gastric digestion. After an ordinary meal gastric diges- 

 tion lasts 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 



