238 ANIMAL HEAT. 



supposition that the carbonic acid is formed in the lungs, or in 

 the extreme vessels of all parts. If their heat is derived from 

 the heat of the blood conveyed to them, the more blood streams 

 through them, the hotter will they be ; if from chemical changes 

 in the blood while in them, the more blood streams through the 

 extreme vessels the greater will be the amount of chemical change, 

 and the greater the extrication of caloric. The quantity of blood, 

 unless constantly renewed, is inefficient, on either supposition. On 

 the first, fresh blood must come incessantly from the lungs with 

 its high temperature; on the second, if not renewed, its chemical 

 changes will cease, having already occurred. 



As it is now generally believed that the oxygen which enters 

 into the blood combines with the carbon, not in the lungs, but in 

 all the extreme vessels, and in them forms carbonic acid, the 

 evolution of heat throughout the body is thus at once explained, 

 it is a mere instance of combustion in the extreme vessels, 

 the union of carbon and oxygen being always attended by an 

 increase of temperature ; and we may equally abstain from 

 troubling ourselves about relative capacities for caloric. The 

 fact of local heats above the temperature of the general mass 

 of blood, proves that heat is evolved by local processes. If 

 arterial blood is made venous, or, more properly, blackened, by gal- 

 vanism, heat is evolved, as I shall presently mention. Those who 

 believe that venous blood has a larger capacity for caloric than 

 the arterial, say that the heat evolved in the minute vessels, by the 

 formation of carbonic acid, does not produce so high a temper- 

 ature as it would, were the capacity of the blood for caloric not 

 lessened by the changed character of the fluid : but, that, when 

 rendered florid again in the lungs, its capacity is again reduced; 

 and, not only is there sufficient caloric to raise the cold air to 98, 

 but the florid blood becomes one or two degrees higher than it 

 was when venous in the right side of the heart. It is evident that, 

 if the chemical changes which occur in the lungs are independent 

 of life, and even take place out of the body, and the evolution 

 of heat is a purely chemical phenomenon, it also will occur in 



c If the combustion thus takes place in the universal extreme vessels, the opinion 

 of Tiedemann and Gmelin, that the use of the liver is to liberate the blood of 

 much carbon without its union with oxygen, will not be the less probable than if 

 the union occurred ordinarily in the lungs. If carbon is copiously removed with- 

 out uniting to oxygen and forming caibonic acid in the blood, we understand why 

 the blood in high temperatures is less dark, is even florid. 



