42i Dr. Spiu'gin's Outlines of a Philosophical 



rial contains a greater proportion of them than venous blood. 

 — The appearances exhibited by the blood in different diseases 

 of the body have been minutely described by different patho- 

 logists, as well as the alteration which takes place in its phy- 

 sical properties: but it must be acknowledged that there is 

 scarcely a fact that can be relied upon that would indicate 

 any decided difference in its chemical constitution. An in- 

 fei'ence is drawn from a few experiments upon the relative 

 composition of the blood in the different periods of life, — that 

 as age advances, the proportion of azote increases ; which is 

 consistent with the opinion of there being more fibrin in the 

 blood of the adult than in that of the infant. Fourcroy in- 

 forms us that he found the blood of the fcetus to contain no 

 fibrin, but a gelatinous substance in its stead. 



Before chemistry arrived at its present comparative degree 

 of perfection, the only mode of examination of the blood re- 

 sorted to, was to subject it to the destructive distillation, as it 

 is called, — which consists in exposing it to the action of heat, 

 and thence in forcing its component parts and its ultimate ele- 

 ments to enter into new combinations, and to yield products 

 altogether different from any thing that can be found in the 

 blood in its natural state. This mode of examination is cer- 

 tainly highly objectionable, more especially if it leads the in- 

 quirer to conclude that the products so obtained exist as 

 such in the blood; but the later and improved mode not only 

 has a greater claim to the appellation of chemical analysis, 

 but is superior to the former in one essential particular, viz. 

 in its proving to a demonstration that the elements of the 

 blood do form new combinations, and thence entirely new pro- 

 ducts. But it at the same time proves its own fallibility and 

 deficiency in another respect, viz. that it affords no ground 

 for supposing that the results of its analysis are absolutely 

 the same with what exists in and compounds the blood in its 

 living state. Compared with the other mode it may be regarded 

 as a closer approximation to the truth, but not the truth itself. 

 Giving it its whole scope and power, this mode informs us that 

 the gi-eat portion of the blood, which it denominates the ani- 

 mal matter, in contradistinction to the salts and gaseous parts, 

 is, as to its ultimate composition, a combination of oxygen, 

 hydrogen, carbon and azote; whilst the various forms under 

 which it exists, are only combinations of these ultimate ele- 

 ments in different proportions. 



Taking the vegetable kingdom in general, this mode of 

 analysis discovers a similar law to obtam, ti>e only exclusion 

 being the azote, whence, chemically speaking, the great dif- 



lerence 



