RESPIRATION. 633 



2 7 '2 2 cubic inches in half an hour, or almost exactly the nor- 

 mal quantity. The second rabbit was placed in exactly the same 

 circumstances, but without artificial respiration. The thermo- 

 meter in the rectum sunk in thirty-five minutes to 905. 



(4.) The experiment was repeated on another rabbit killed by 

 the essential oil of bitter almonds. In half an hour, the ther- 

 mometer in the rectum sunk to 90. The carbonic acid evolved 

 during the artificial respiration was 28-275 cubic inches, or some- 

 what more than the normal quantity. 



If the accuracy of these experiments may be depended on, it 

 seems to follow from them, that the chemical changes going on 

 in the lungs are not the source of the heat of the animal. But 

 it must not be concealed that they were repeated and varied by 

 M. Legallois, who obtained different results. He found, in most 

 cases, that when artificial respiration is kept up in a dead ani- 

 mal, the animal heat continues higher than when the lungs are 

 not inflated. The result of his experiments was, that in general 

 the heat of animals is directly proportional to the quantity of 

 oxygen which they consume in a given time.* 



The experiments of Legallois agree well with those of Des- 

 pretz,f which are the most elaborate hitherto made upon respi- 

 ration, and of which I shall now proceed to give an account. 



13. According to Dr Black, part of the latent heat of the air 

 inspired becomes sensible ; and of course the temperature of the 

 lungs, and the blood that passes through them, must be raised ; 

 and the blood thus heated, communicates its heat to the whole 

 body. This opinion was ingenious, but it was liable to an un- 

 answerable objection : for if it were true, the temperature of the 

 body ought to be greatest in the lungs, and to diminish gradual- 

 ly as the distance from the lungs increases, which is not true. 

 The theory, in consequence, was abandoned even by Dr Black 

 himself, at least he made no attempt to support it. 



Dr Crawford, who considered all the changes operated by res- 

 piration as taking place in the lungs, accounted for the origin of 

 the animal heat almost precisely in the same way with Dr Black. 

 According to him, the oxygen gas of the air combines in the 

 lungs with the carbon emitted by the blood. During this com- 

 bination, the oxygen gives out a great quantity of caloric, with 



Ann de Chim et de Phys. xxvi. 342. 

 t Ibid xxvi. 337. 



