INFLUENCE OF NERVOUS SYSTEM ON DIGESTIVE GLANDS 405 



appetite in digestion, a truism in treatment which thus receives 

 for the first time a rational explanation. The influence of good- 

 humour upon nutrition, which experience has crystallized into the 

 proverb ' Laugh and grow fat,' has also been shown to depend 

 in great part, at least upon a beneficial action on the digestive 

 functions, both motor and chemical. The movements of a cat's 

 stomach and intestines have been observed to cease when the 

 animal became angry or excited by unpleasant emotions; and in a 

 dog whose gastric glands were pouring out a copious psychical 

 secretion in response to a sham meal, secretion stopped abruptly 

 when the animal's wrath was awakened by what is probably to the 

 normal dog the most specifically ' adequate ' stimulus for the emotion 

 of anger the sight of a cat which he was restrained from chasing. 



By means of experiments with the miniature stomach it has been 

 further shown. that each kind of food has its own characteristic 

 curve of gastric secretion. With flesh diet the maximum rate of 

 secretion occurs during the first or second hour, and in each of the 

 first two hours the quantity of juice furnished is approximately 

 the same. With bread diet we have always a sharply-indicated 

 maximum in the first hour, and with milk a similar one during the 

 second or the third hour (Fig. 163). The juice secreted on different 

 diets also differs in digestive power i.e., in the amount of protein 

 which a given quantity of it will digest in a given time. ' Bread 

 juice ' is much stronger in ferment than ' meat juice/ and ' meat 

 juice ' somewhat stronger than ' milk juice ' (Fig. 164). But 

 ' meat juice ' has a higher acidity than ' bread juice,' ' milk juice ' 

 being intermediate. These differences do not necessarily indicate 

 that the gastric mucous membrane responds in a specific way to 

 each kind of food substance, as suggested by Pawlow. They may 

 depend on several circumstances, and particularly on this that the 

 quantity, though not the quality, of the psychical or ' appetite ' 

 juice is related to the relish with which the animal eats the food. 

 The products formed in the digestion of the different foods by the 

 psychical juice may therefore be different in nature and amount, 

 and thus the quantity of the gastric hormone which determines the 

 secondary secretion may vary with the food. 



The young mammal, like the adult, secretes gastric juice before 

 the food reaches the stomach. In puppies from one to eighteen 

 days old sham feeding (sucking the teats of the mother after'an 

 oesophageal fistula has been made in the younger animals and a 

 double oesophageal and gastric fistula in the older) causes a liquid 

 with the properties of gastric juice to gather in the stomach. This 

 power, then, is a congenital one. The individual does not gain it 

 by experience; it comes into the world with him (Cohnheim). 



The Influence of Nerves on the Pancreas. Like the stomach, the 

 pancreas receives secretory fibres through the vagus. These are 



