72 PROXIMATE PRINCIPLES OF THE FIRST CLASS. 



animal frame depends upon the relative quantity of all the ingre- 

 dients of the fluids, as well as on the constitution of the solids 

 themselves; and the chloride of sodium, as one ingredient among 

 many, influences these phenomena to a great extent, though it does 

 not regulate them exclusively. 



It exerts also an important influence on the solution of various 

 other ingredients, with which it is associated. Thus, in the blood 

 it increases the solubility of the albumen, and perhaps also of the 

 earthy phosphates. The blood-globules, again, which become dis- 

 integrated and dissolved in a solution of pure albumen, are main- 

 tained in a state of integrity by the presence of a small quantity of 

 chloride of sodium. 



It exists in the following proportions in several of the solids and 

 fluids :' 



QUANTITY OF CHLORIDE OF SODIUM IN 1,000 PARTS IN THE 



Muscles .... 2 Bile .... 3.5 



Bones . " . . . 2.5 Blood .... 4.5 



Milk .... 1 Mucus .... 6 



Saliva . , . . . 1.5 Aqueous humor . . 11 



Urine .... 3 Vitreous humor . . 14 



In the blood it is rather more abundant than all the other saline 

 ingredients taken together. 



Since chloride of sodium is so universally present in all parts of 

 the body, it is an important ingredient also of the food. It occurs, 

 of course, in all animal food, in the quantities in which it naturally 

 exists in the corresponding tissues; and in vegetable food also, 

 though in smaller amount. Its proportion in muscular flesh, 

 however, is much less than in the blood and other fluids. Conse- 

 quently, it is not supplied in sufficient quantity as an ingredient of 

 animal and vegetable food, but is taken also by itself as a condi- 

 ment. There is no other substance so universally used by all races 

 and conditions of men, as an addition to the food, as chloride of 

 sodium. This custom does not simply depend on a fancy for grati- 

 fying the palate, but is based upon an instinctive desire for a sub- 

 stance which is necessary to the proper constitution of the tissues 

 and fluids. Even the herbivorous animals are greedy of it, and if 

 freely supplied with it, are kept in a much better condition than 

 when deprived of its use. 



The importance of chloride of sodium in this respect has been 

 well demonstrated by Boussingault, in his experiments on the 



1 Robin and Verdeil. 



