Medicine. 23 5 



this caloric is not only sufficient to maintain the 

 temperature of the body, but also to carry off the 

 new formed water in the state of vapour, as 

 well as the carbonic acid, and to raise con- 

 siderably the temperature of the air expired. 

 According to the opinion, therefore, of these 

 philosophers, the whole of the caloric which sup- 

 ports the heat of the body is extricated in the 

 lungs. But on this hypothesis the question will 

 arise, how it happens that the heat of each indi- 

 vidual is maintained nearly the same in every part 

 of his body? To explain this. Dr. Crawford en- 

 deavoured to prove, by well devised experiments, 

 that the capacities for containing caloric in arterial 

 and venous blood, are nearly as il.5 to 10; that 

 is to say, if it require a quantity of caloric, repre- 

 sented by 11.5, to heat a pound of arterial blood 

 from zero to 30° . it will only require a quantity 

 as 10, to heat a pound of venous blood from zero 

 to 30°. 



On these experiments the following conclusions 

 were formed. Oxygen gas is decomposed in the 

 lungs, in consequence of the affinity of the carbon 

 and hydrogen of the blood for oxygen being- 

 greater than that of oxygen for caloric, or of the 

 carbon and hydrogen for the blood. In proportion 

 as the oxygen unites w^ith the hydrogen and car- 

 bon, water and carbonic acid are formed; the 

 caloric combines with the venous blood, which, in 

 losing its carbon and hydrogen, becomes arterial, 

 and has its capacity for containing caloric immedi- 

 ately augmented. The blood, now become arte- 

 rial, in its circulation through the body, gradually 

 absorbs carbon and hydrogen, repasses to the ve- 

 nous state, and sets free a portion of caloric In pro- 

 portion as its capacity for containing it is di- 

 minished. According to this doctrine, therefore^ 

 thie almost uniform temperature in all parts of tbi? 



