INTRODUCTION". 51 



Thus lime, dissolved in water, if brought into contact with car- 

 bonic acid, alters its condition, and takes part in the formation of 

 an insoluble substance, carbonate of lime, which is thrown down 

 as a deposit. A knowledge of such chemical reactions as these is 

 necessary to the anatomist, since it is by them that he is enabled to 

 recognize the inorganic substances, forming a part of the animal 

 body. 



It is important to observe, however, that a knowledge of these 

 reactions is necessary to the anatomist only in order to enable him 

 to judge of the presence or absence of the inorganic substances to 

 which they belong. It is the object of the anatomist to make him- 

 self acquainted with every constituent part of the body. Those 

 parts, therefore, which cannot be recognized by their form and 

 texture, he distinguishes by their chemical reactions. But after- 

 ward, he has no occasion to decompose them further, or to make 

 them enter into new combinations ; for he "only wishes to know 

 these substances as they exist in the body, and not as they may exist 

 under other conditions. 



The unorganized substances which exist in the body as compo- 

 nent parts ^of its structure, such as chloride of sodium, water, phos- 

 phate of lime, &c., are called the proximate principles of the body. 

 Mingled together in certain proportions, they make up the animal 

 fluids, and associated also in a solid form, they constitute the tissues 

 and organs, and in this way make up the entire frame. 



Anatomy makes us acquainted with all these component parts of 

 the body, both solid and fluid. It teaches us the structure of the 

 body in a state of rest ; that is, just as it would be after life had 

 suddenly ceased, and before putrefaction had begun. On the other 

 hand, Physiology is a description of the body in a state of activity, 

 It shows us its movements, its growth, its reproduction, and the 

 chemical changes which go on. in its interior; and in order to com- 

 prehend these, we must know, beforehand, its entire mechanical, 

 textural, and chemical structure. 



It is evident, therefore, that the description of i\Q proximate prin- 

 ciples, or the chemical substances entering into the constitution of 

 the body, is, strictly speaking, a part of Anatomy. But there are 

 many reasons why this study is more conveniently pursued in con- 

 nection with Physiology ; for some of the proximate principles are 

 derived directly, as we shall hereafter show, from the external world, 

 and some are formed from the elements of the food in the process 

 of digestion ; while most of them undergo certain changes in the 



