ANIMAL HEAT. 239 



the blood out of the body. Accordingly Sir C. Scudamore, 

 exposing two portions of the same blood, under the same circum- 

 stances, the one to atmospheric air, the other to oxygen, found 

 the temperature of the portion exposed to oxygen eight degrees 

 higher at the end of eight minutes than that of the other. 



It is possible that other chemical changes, which incessantly 

 go on throughout the frame, also occasion heat to be evolved. 



A host of circumstances show that our temperature depends 

 upon respiration, and therefore upon chemical changes. 



In high temperatures we have less necessity for the evolution 

 of heat; in low temperatures, more. Accordingly, in the former, 

 the arterial blood remains arterial, is nearly as florid in the 

 veins as in the arteries d , and the inspired air is less vitiated; in 

 low temperatures, the venous blood is extremely dark, and the 

 inspired air more vitiated. e Some have imagined that the body 

 remains at its standard high temperature by the refrigeration of 

 the evaporating sweat. But, though this must contribute, it is not 

 the sole cause f ; for frogs lose as much proportionally to their 

 size by evaporation as any other animal, yet they follow pretty 

 closely the surrounding temperature. Whenever, on the other 

 hand, the body itself heightens its temperature, as in fever, more 

 oxygen is consumed by the lungs g; (in the cold stage of fevers 

 we saw that less was consumed.) The temperature of the va- 

 rious classes of animals, and their vitiation of the air, are always 

 proportional ; and inverse to the length of time they can live 

 without air. 



d Dr. Crawford, 1. c. p. 387. sq. Dr. De la Roche, 1. c. 



c Dr. Crawford, ib. " C. Ferd. Becker, De JE/ectibus caloris etfrigoris ex- 

 terni in c. h. Gott. 1802. 4to. ; and Wm. Fr. Bauer, On the same subject. 

 IB EOI. (BOTH HONOURED WITH THE ROYAL PRIZE.) 



Mich. Skjelderup, Dissert, sistens vim frigojis incitantem. Hafn. 1803. Svo." 



Yet, in the account of Sir Astley Cooper's experiments, quoted at p. 235., it 

 is mentioned that a puppy and a kitten, some weeks old, were placed nearly to 

 the mouth in iced water, till they died ; and that the blood of the lips, nose, 

 toes, mesentery, and left side of the heart, was of a fine vermilion hue. The 

 colour of the venous blood is not mentioned. I should presume it was very dark, 

 but that the oxygen, from the great coldness of the air inspired, was so effective 

 in withdrawing the carbonic acid, that the arterial blood was, on this account, 

 unusually florid. 



f Dr. Edwards, 1. c. p. 488. 



6 See supra, p. 222. 



