80 IMMEDIATE PRINCIPLES OF THE TISSUES. 



of lime and other salts which have been spoken of as immediate 

 principles ; unless a diminished amount of the phosphate of lime is 

 taken in the food, or the bones, especially, need an increased amount 

 of it as in rachitis and malacosteon. 



Second Group. 

 CLASS THIRD. 



ORGANIC SUBSTANCES, OR COAGULABLE PRINCIPLES. 



The organic immediate principles constitute the greater part of 

 the mass of the organism; those of the first class entering it in 

 smaller, and those of the second in very small proportion. These 

 are all nitrogenized compounds, or compounds of carbon, hydrogen, 

 oxygen, and nitrogen, and all of neutral reaction. 



It is, however, a peculiarity of this class of principles that they 

 have not a definite chemical composition, as is the case with the other 

 classes. It is, indeed, constantly varying, though within certain 

 rather narrow limits, the variation rarely exceeding 1 per cent, in 

 respect to either of the chemical elements entering into their com- 

 position. It follows, of course, that the combinations of these prin- 

 ciples with other substances (as acids, alkalies, &c.) cannot be definite 

 and uniform compounds; e. g. sulphate of copper and albumen being 

 mixed, the salt is decomposed, and its two elements combine with 

 the albumen ; yet the result is neither sulphate of albumen, nor 

 albuminate of copper, in definite proportions. 1 (Robin and Verdeil) 



If, therefore, albumen, fibrine, &c., are constantly varying in their 

 own precise composition, much less is it true that these two sub- 

 stances are always identical in composition. And yet two analyses 

 of them (e. g. of fibrine) may not be more nearly identical in their 

 results than an analysis of the former as compared with one of the 

 latter. 



Most of the earthy salts phosphates, carbonates, oxalates, silex, 

 and the silicates unite with these substances; hence, whenever 

 concretions are formed by the former, a certain quantity of the 

 organic substances is fixed and retained in them. This union is, 

 however, more feeble than that with the metallic salts, and hence is 



1 Hence the difficulty of distinguishing these principles from each other by the 

 reactions of mercury, tin, copper, &c. 



