AND UPON THE VITAL PROPERTIES OF BLOOD. 1041 



depurated, as in health, by the elimination of 

 sweat, urine, and other excretions, which, being 

 retained, must still further derange its vital pro- 

 perties. If at this stage of the disease blood be 

 drawn from a vein, or even from the temporal 

 artery, it is found to be unusually dark coloured, 

 as might naturally be inferred from the livid hue 

 of the surface, especially in cases of great de- 

 pression, during which it is sometimes difficult 

 to obtain a flow of blood, owing to its extreme 

 viscidity. 



If, then, it be true, that animal heat is the 

 agent by which blood is formed, converted into 

 the different organs, and maintains them in a 

 state of healthy activity, it is evident that what- 

 ever tends to diminish the supply of this important 

 principle must impair the healthy properties of 

 the blood, and thus lay the foundation of disease. 

 The essential symptoms are the same in every 

 variety of fever, whether brought on by the 

 abstraction of caloric from the influence of cold 

 and moisture, its expenditure by over exertion, 

 or by the various causes which diminish respira- 

 tion. But as they are most distinctly marked 

 in the intermittent form of the disease, I shall 

 proceed to shew that all the morbid phenomena 

 which characterize that type may be traced to a 

 reduction of temperature, and a vitiated condition 

 of the blood. 



In the first place, that the shuddering or spas- 



