PROXIMATE PRINCIPLES OF THE FIRST CLASS. 69 



CHAPTER II. 



PKOXIMATE PRINCIPLES OF THE FIRST CLASS. 



THE proximate principles of the first class, or those of an inor- 

 ganic nature, are very numerous. Their most prominent characters 

 have already been stated. They are all crystallizable, and have a 

 definite chemical composition. They are met with extensively in 

 the inorganic world, and form a large part of the crust of the earth. 

 They occur abundantly in the different kinds of food and drink ; 

 and are necessary ingredients of the food, since they are necessary 

 ingredients of the animal frame. Some of them are found universally 

 in all parts of the body, others are met with only in particular 

 regions ; but there are hardly any which are not present at the 

 same time in more than one animal solid or fluid. The following 

 are the most prominent of them, arranged in the order of their 

 respective importance. 



1. WATER. Water is universally present in all the tissues and 

 fluids of the body. It is abundant in the blood and secretions, 

 where its presence is indispensable in order to give them the fluidity 

 which is necessary to the performance of their functions; for it 

 is by the blood and secretions that new substances are introduced 

 into the body, and old ingredients discharged. And it is a neces- 

 sary condition both of the introduction and discharge of substances 

 naturally solid, that they assume, for the time being, a fluid form ; 

 water is therefore an essential ingredient of the fluids, for it holds 

 their solid materials in solution, and enables them to pass and repass 

 through the animal frame. 



But water is an ingredient also of the solids. For if we take a 

 muscle or a cartilage, and expose it to a gentle heat in dry air, it 

 loses water by evaporation, diminishes in size and weight, and be- 

 comes dense and stiff. Even the bones and teeth lose water by 

 evaporation in this way, though in smaller quantity. In all these 

 solid and semi-solid tissues, the water which they contain is useful 



