PROXIMATE PRINCIPLES IN GENERAL. 67 



in the general condition of the body, as a whole, is accompanied by 

 a corresponding variation, more or less pronounced, in the consti- 

 tution of its different parts. This constitution is consequently of 

 a very different character from the chemical constitution of an 

 oxide or a salt. Whenever, therefore, we meet with the quanti- 

 tative analysis of an animal fluid, in which the relative quantity 

 of its different ingredients is represented in numbers, we must 

 understand that such an analysis is always approximative, and not 

 absolute. 



The proximate principles are naturally divided into three differ- 

 ent classes. 



The first of these classes comprises all the proximate principles 

 which are purely INORGANIC in their nature. These principles are 

 derived mostly from the exterior. They are found everywhere, in 

 unorganized as well as in organized bodies ; and they present them- 

 selves under the same forms and with the same properties in the 

 interior of the animal frame as elsewhere. They are crystallizable, 

 and have a definite chemical composition. They comprise such 

 substances as water, chloride of sodium, carbonate and phosphate 

 of lime, &c. 



The second class of proximate principles is known as CRYSTAL- 

 LIZABLE SUBSTANCES OF ORGANIC ORIGIN. This is the name given 

 to them by Kobin and Yerdeil, 1 whose classification of the proxi- 

 mate principles is the best which has yet been offered. They are 

 crystallizable, as their name indicates, and have a definite chemical 

 composition. They are said to be of " organic origin," because they 

 first make their appearance in the interior of organized bodies, and 

 are not found in external nature as the ingredients of inorganic 

 substances. Such are the different kinds of sugar, oil, and starch. 



The third class comprises a very extensive and important order 

 of proximate principles, which go by the name of the ORGANIC 

 SUBSTANCES proper. They are sometimes known as " albuminoid" 

 substances or " protein compounds." The name organic substances 

 is given to them in consequence of the striking difference which 

 exists between them and all the other ingredients of the body. The 

 substances of the second class differ from those of the first by their 



1 Chiuiie Anatomique et Physiologique. Paris, 1853. 



