CHEMISTRY OF MAN. 



CHAPTER I. 



ON THE PROXIMATE ANALYSIS OF COMPOUND ANIMAL 



SUBSTANCES. 



Zoocliemical analyses are instituted for the purpose of ascer- 

 taining, either quantitatively or qualitatively, the proximate or 

 ultimate constituents of animal substances. It is requisite in 

 physiological and pathological chemistry that equal attention 

 should he paid to both these modes of investigation, for there 

 is this great distinction between the chemistry of inorganic and 

 of organic bodies, that in the former case the determination of 

 the proximate principles can be inferred from that of the ulti- 

 mate constituents, while in the latter case no such rule holds 

 good, and the two species of analyses (the proximate and ulti- 

 mate) must be conducted separately and distinctly. In the in- 

 vestigation of the variations in the constitution of the blood, 

 whether dependent during health upon age, sex, or temperament, 

 or during disease upon various pathological states of the system ; 

 in the determination of the constituents of milk, sweat, or pus ; 

 in the detection of sugar, urea, or bilin, in the various fluids, 

 in which normally they are absent ; in these and all similar cases 

 ultimate analysis Avill avail us nothing, and we must have re- 

 course to tests for the substances themselves, or for some of 

 their proximate principles. Investigations of this nature will, 

 moreover, do very little for the advancement of pathological or 

 physiological knowledge, unless they are Adewed in relation to 

 a considerable number of similar analyses, conducted under pre- 

 cisely corresponding circumstances ; for in consequence of the 

 necessary variation that is constantly occurring in the animal 

 fluids, each analysis can only be regarded as the representative of 



