PEOXIMATE PRINCIPLES. 21 



a full consideration of which, in connection with special 

 functions, would be out of place, as well as many points in 

 physiological chemistry, showing the relations of the different 

 elements to nutrition, etc. ; hence is desirable, as an intro- 

 duction to physiology proper, a brief review of the prox- 

 imate principles of the economy. In this introduction it is 

 not proposed to treat exhaustively of physiological chemistry. 

 Such principles as will demand, from their connection with 

 special functions, extended consideration in another place, 

 are omitted or simply alluded to, as well a some which have 

 a very unimportant or obscure function. 



If we were to study the constitution of the body from a 

 purely chemical point of view, it would be divided into 

 elementary substances, or those which are absolutely incapa- 

 ble of further subdivision. In this way we should lose all 

 distinction between organic matters and those which enter 

 indifferently into the composition of all bodies in Nature, 

 whether inert or endowed with vital properties. After 

 having thus ascertained the ultimate constitution of the 

 organism, we have learned all that is possible by this method ; 

 for we are already familiar with the properties and be- 

 havior of elementary matter, as obtained from the inorganic 

 kingdom. 



In physiological chemistry this method is inadmissible. 

 The substances which are presented for our study in the 

 living organism are endowed with vital properties. Their 

 ultimate composition is of little consequence compared with 

 a knowledge of the laws which regulate their behavior, not 

 as elements, but as constituents of an elaborate vital organi- 

 zation. 



"We can separate from the organism of animals substances 

 of a peculiar nature which are never found in the inorganic 

 world. These demand our special consideration. If we 

 attempt to study them by the ordinary chemical processes of 

 analysis, they are destroyed and lose their properties as 

 organic principles. 



