THE SIGNIFICANCE OF THE FOOD-STUFFS 725 



course of metabolism of the proteins. It is possible to obviate this 

 acid intoxication by administering sodium carbonate with the food. 

 This admixture, however, only suffices to prolong the life of the 

 animal for a short time. It is evident therefore that the inorganic 

 constituents of the food, although yielding no energy to the body, 

 are as essential for the maintenance of life as the energy-yielding 

 food-stuffs, namely, proteins, carbohydrates, and fats. In the course 

 of this work we shall have occasion to study the intimate dependence 

 of the functions of various tissues, such as skeletal and heart muscle, 

 on the presence of salts in normal proportions in the fluids with 

 which they are bathed. Animals in a state of salt hunger show 

 by the disorders of digestion which occur that the presence of salts 

 is equally requisite for the due performance of the processes of 

 secretion and absorption. Towards the end of the experiment the 

 animal vomits its food, which shows no signs of digestion even 

 when it has lain some hours in the stomach. Forster has shown 

 that in salt-hunger the body is continually giving off inorganic con- 

 stituents in the urine. The amount of these is smallest when it is 

 supplied richly with organic food-stuffs. It seems that the salts 

 of the body exist in a state of unstable combination with the tissue 

 constituents, especially the proteins. If the amount of food supplied 

 is insufficient, the animal lives on its own tissues, thus setting free 

 salts which appear in the urine. The loss of salts to the body will 

 therefore be in direct proportion to the degree in which the animal is 

 living at the expense of its own tissues. 



