634" FUNCTIONS OF ANIMALS. 



which it had been combined ; and this caloric is not only suffi- 

 cient to support the temperature of the body, but also to carry off 

 the new-formed water in the state of vapour, and to raise consi- 

 derably the temperature of the air inspired. According to this 

 philosopher, then, the whole of the caloric which supports the 

 temperature of the body is evolved in the lungs. His theory ac- 

 cordingly was liable to the same objection with Dr Black's ; but 

 Dr Crawford obviated it in the following manner : He found 

 that the specific caloric of arterial blood was 1-0300, while that 

 of venous blood was only 0-8928. Hence, he concluded, that the 

 instant venous blood is changed into arterial blood, its specific 

 caloric increases ; consequently it requires an additional quan- 

 tity of caloric to keep its temperature as high as it had been 

 while venous blood. This addition is so great, that the whole 

 new caloric evolved is employed : therefore, the temperature of 

 the lungs must necessarily remain the same as that of the rest of 

 the body. During the circulation, arterial blood is gradually 

 converted into venous ; consequently, its specific caloric dimi- 

 nishes, and it must give out heat. This is the reason that the 

 temperature of the extreme parts of the body does not diminish. 



Lavoisier, who was the first person that ascertained the com- 

 position of carbonic acid gas, considered the phenomena of res- 

 piration as analogous to combustion. Now, when oxygen com- 

 bines rapidly with carbon or hydrogen, combustion takes place 

 and heat is evolved. The evolution of heat in the lungs by the 

 combination of the carbon of the blood with the oxygen of the 

 atmosphere is analogous to combustion. 



(1.) It follows, from the experiments of M. Despretz, that du- 

 ring the combustion of an avoirdupois pound of carbon, the 

 quantity of heat evolved is sufficient to melt 104*2 Ibs. of ice. 

 Now, if the latent heat of water be 140, 104-2 Ibs. of ice will 

 require to melt 14,588 degrees of heat, or, in other words, the 

 heat evolved during the combustion of a pound of carbon would 

 heat a pound of water 14,588. 



(2.) The oxygen gas requisite to consume a pound of carbon 

 amounts to 2| Ibs., which is equivalent to 55,082 cubic inches 

 at the temperature of 60. This oxygen gas combines with car- 

 bon, and is converted into its own volume of carbonic acid gas. 



(3.) 55,082 cubic inches of oxygen gas when converted into 

 carbonic acid gas give out 14,588 of heat; consequently, every 



