OF DR. J. DAVY. 549 



the difference is in some cases 3 ; which I have 

 verified by repeated experiments. He also 

 found that the blood of a spaniel bitch was 104 

 in the right side of the heart, but 107 in the left 

 ventricle and pleura; thus demonstrating that 

 the lungs have a higher temperature than other 

 parts of the body, which Cullen had ironically 

 said ought to be the case if animal heat were the 

 effect of respiration. And as Haycraft, Dela- 

 rive, and Marcet had shown that equal volumes 

 of the different gases have the same capacity for 

 heat, Davy proved that it is nearly the same in 

 arterial and venous blood ; thus sweeping away 

 all the crude speculations founded on the erro- 

 neous experiments of Crawford, who represented 

 the capacity of oxygen gas as 4.7, compared with 

 carbonic acid, which he made 1.6 ; that of arterial 

 blood as 1.03, and venous blood as *89. Yet Dr. 

 Davy maintains that animal heat is owing to the 

 fixation or condensation of oxygen in the blood, 

 and to the combinations into which it enters in 

 the circulation. (Physiological and Anat. Re- 

 searches, vol. ii. p. 171.) 



Miiller observes, that the formation of car- 

 bonic acid in the capillary vessels of the body 

 explains why the lungs are not warmer than any 

 other part of the system. (Elements, p. 333.) 

 But we have seen from the excellent observations 

 of Davy, that the pleura, which surrounds the 

 lungs, and the blood that comes immediately 



