232 PHYSIOLOGY OF ALIMENTATION. 



Milk and water are also independent excitants of the gastric 

 i^tion. We find in this another reason for the use of water 

 with meals. Milk has from the earliest times been considered 

 an easily digested food for children and invalids. Not only 

 does this fluid cause a secretion of gastric juice, but, as has 

 been shown above, a weaker gastric juice and a smaller 

 quantity of pancreatic juice are poured out on milk than on 

 an equivalent amount of nitrogen contained in any other 

 food. The work performed by these digestive glands is 

 therefore less, and the saving of energy, in consequence, is 

 greater than when meat or bread, for example, is fed. The 

 amount of work which the organism does in order to assimi- 

 late a certain amount of nutriment must always be sub- 

 tracted from the energy value of the food itself. This is not 

 ordinarily considered in determining the value of various 

 foods. We have seen above, however, that equivalent 

 weights of nitrogen in the proteins of meat, bread, and 

 milk cost the organism different amounts of glandular 

 energy. 



Fat inhibits the secretion of gastric juice. We find in this 

 the explanation of the fact that its presence in a mixed meal 

 impedes the rate of digestion, and hence is contraindicated in 

 cases of feeble digestion, while it works excellently in cases 

 of hyperacidity and hypersecretion. The alkalies and alka- 

 line salts belong in this group of substances which inhibit the 

 secretions of the gastric mucosa and the pancreas. 



We have learned from experiments detailed above the 

 uselessness of mechanical stimulation of the gastric mucosa 

 in bringing about a secretion of gastric juice. Neither 

 mechanical stimulation through coarse food or by means 

 of special apparatus, such as an inflatable balloon, can there- 

 fore be looked upon as rational treatment for those gastric 

 disorders which are characterized by deficient secretion of 

 juice. Care must be taken not to confound this statement 

 with the relation between mechanical stimulation and the 

 motor functions of the stomach. 



