48 INORGANIC PROXIMATE PRINCIPLES. 



however, there is a striking difference between the carnivorous and 

 many herbivorous animals. The carnivora receive a fully sufficient 

 supply with their natural food, and invariably show a repugnance to 

 salt itself, as well as to salted meats. On the other hand, the horse, 

 and more especially the ruminating animals, have an instinctive desire 

 for salt, and greedily devour it, wh.en offered to them, in addition to 

 that naturally contained in the vegetable matters of their food. It is 

 well known with what avidity the cattle, sheep, and all kinds of deer 

 frequent the saline springs or " salt licks" of the United States ; and it 

 is shown by common experience that a liberal supply of salt is important 

 for the healthy nutrition and development of these animals in the 

 domesticated condition. 



The same fact has been demonstrated in a more exact manner by the 

 experiments of Boussingault on the ox. 1 This observer made a series 

 of comparative investigations upon the growth of two sets of bullocks 

 selected from animals of the same age and vigor, and supplied equally 

 with an abundance of ordinary nutritious food, those of one set, how- 

 ever, receiving in addition each 34 grammes of salt per day. At the 

 end of six months the difference in the aspect of the animals of the two 

 sets began to be distinctly evident, and became more marked as time 

 went on. The experiment lasted for a year, and at the end of that time 

 both sets of animals had on the average equally increased in weight ; 

 but those fed with ordinary food alone presented a rough and tangled 

 hide and a dull, inexcitable disposition, while in those which had re- 

 ceived the additional ration of salt the hide was smooth and glistening 

 and the general appearance was vigorous and animated. While these 

 animals, therefore, may subsist for a time without inconvenience upon 

 the salt naturally contained in their food, an additional quantity is 

 required to maintain the system in good condition for an indefinite 

 period. 



There is a similar necessity for salt as an addition to the food of the 

 human species. No other substance is so universally used as a condi- 

 ment by all races and conditions of men. This custom does not depend 

 simply on a fancy for gratifying the palate, but is based upon an in- 

 stinctive demand of the system for a substance which is necessarj^ for 

 the full performance of its functions. Beside its other properties, it no 

 doubt acts in a favorable manner by exciting the digestive fluids, and 

 assisting in this way the solution of the food. For food which is taste- 

 less, however nutritious it may be in other respects, is taken with 

 reluctance and digested with difficulty ; while the attractive flavor which 

 is developed by cooking, and by the addition of salt and other condiments 

 in proper proportion, excites the secretion of the saliva and gastric juice, 

 and facilitates consequently the whole process of digestion. The sodium 

 chloride is then taken up by absorption from the intestine, and is de- 

 posited in various quantities m different parts of the body. 



1 Cliimie Agricole. Paris, 1854, p. 251. 



