PHYSIOLOGY OF THE DIGESTIVE GLANDS 



471 



expected that the quantity of the psychic secretion will not be the same 

 in different individuals. It has been observed by Pavlov, for example, 

 to vary considerably in the case of dogs, and it is very likely that it will 

 vary still more in man, with his more highly complicated nervous system. 

 In no case could Carlson observe any secretion of gastric juice to be pro- 

 duced by having his patient chew on indifferent substances, or by stim- 

 ulating the nerve endings in the mouth by substances other than those 

 directly related to food. 



In man the rate of secretion is proportional to the palatability of the 

 food, the smallest amount, during twenty minutes' mastication of pal- 

 atable food, being 30 c.c. and the largest 150 c.c., in a series of 156 obser- 

 vations. A typical curve showing the amount of the secretion is given 

 in Fig. 149. To construct this curve the gastric juice was collected diy- 



\ 



25' 



30' 



50* 



55 



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.) 



ing five-minute intervals while the man was chewing a meal of average 

 composition and of his own choice. An interesting feature depicted on 

 this curve is that the secretion rate was highest in the last five-minute 

 period, this being the time during which the dessert was being taken, 

 for which this man had a great relish. Quite clearly there was a direct 

 relation between the rate of the secretion of the appetite juice and the 

 palatability of the food. It will further be observed that it took only 

 from fifteen to twenty minutes after discontinuing the chewing before 

 the juice returned to its original level. 



The practical application of these facts in connection with the hygiene 

 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- 



