PROXIMATE PRINCIPLES IN GENERAL. 35 



other by the help of certain chemical manipulations, such as evapora- 

 tion, solution, crystallization, and the like, it might be supposed that 

 every substance which could be extracted from an organized solid or 

 fluid, by chemical means, should be considered as a proximate princi- 

 ple. That, however, is not the case. A proximate principle is properly 

 defined to be any substance, whether simple or compound, chemically 

 speaking, which exists, under its own form, in the animal solid or fluid, 

 and which can be extracted by means which do not alter or destroy its 

 chemical properties. Lime phosphate, for example, is a proximate 

 principle of bone, but phosphoric acid is not so, since it does not exist 

 as such in the bony tissue, but is produced only by the decomposition 

 of the calcareous matter ; still less phosphorus, which is obtained only 

 by the decomposition of the phosphoric acid. 



Proximate principles may, in fact, be said to exist in all solids or 

 fluids of mixed composition, and may be extracted from them by the 

 same means as in the case of the animal tissues or secretions. Thus, in 

 a watery solution of sugar, we have two proximate principles, namely: 

 first, the water, and secondly, the sugar. The water may be separated 

 by evaporation and condensation, after which the sugar remains behind, 

 in a crystalline form. These two substances have, therefore, been sim- 

 ply separated from each other by the process of evaporation. They 

 have not been decomposed, nor their chemical properties altered. On 

 the other hand, the hydrogen and oxygen of the water were not proxi- 

 mate principles of the original solution, and did not exist in it under 

 their own forms, but only in a state of combination; forming, in this 

 condition, a fluid substance (water), endowed with sensible properties 

 entirely different from theirs. If we wish to ascertain, accordingly, the 

 nature and properties of a saccharine solution, it will afford us but 

 little satisfaction to extract its ultimate chemical elements; for its 

 nature and properties depend not so much on the presence in it of the 

 ultimate elements, oxygen, hydrogen, and carbon, as on the particular 

 forms of combination, namely, water and sugar, under which they are 

 present. 



It is very essential, therefore, that in extracting the proximate prin- 

 ciples from the animal body, only such means should be adopted as will 

 isolate the substances already existing in the tissues and fluids, without 

 decomposing them, or altering their nature. A neglect of this rule 

 would lead to erroneous results in the pursuit of physiological chemis- 

 try; for by subjecting the animal tissues to the action of acids and 

 alkalies, of prolonged boiling, or of too intense heat, we might obtain, 

 at the end of the analysis, substances which would not be, properly 

 speaking, proximate principles, but only the remains of an altered and 

 disorganized material. Thus, the fibrous tissues, if boiled steadily for 

 thirty-six hours, dissolve, for the most part, at the end of that time, 

 in the boiling water; and on cooling the whole solution solidifies into a 

 homogeneous, jelly-like substance, which has received the name of 

 gelatine. But this gelatine does not really exist in the body as a 



