538 LEADING POINTS IN 



Columbus, not covered with an imaginary Terra 

 Australis, or fancied Atalantis,' 1 c. (Philosophy 

 of Life, p. 148, 156, 384.) Dr. Southwood Smith 

 also observes, that " whether the blood acquires 

 something from the atmosphere which is es- 

 sential to life, or part with something incom- 

 patible with life, is wholly unknown." (Philo- 

 sophy of Health, vol. ii. p. 436.) 



Among those physiologists who regard respira- 

 tion as the source of animal temperature, it is still 

 undecided what proportion of the oxygen con- 

 sumed is converted into carbonic acid ; whether 

 the combination of oxygen with carbon takes 

 place in the air cells of the lungs, as maintained 

 by Black, Crawford, Lavoisier, Ellis, and Dalton; 

 or in the general course of the circulation, as sup- 

 posed by Lagrange, Hassenfratz, Edwards, and 

 some others. With the exception of Priestley, the 

 early experimenters concluded that nearly all the 

 oxygen absorbed during respiration, was expired 

 in the form of carbonic acid. But it was soon after 

 discovered by Crawford and Lavoisier that about 

 25 per cent, of theoxygen consumed disappeared ; 

 from which they concluded that it united with 

 hydrogen to form water. Similar results were 

 obtained by Sir H. Davy, from numerous ex- 

 periments on himself; for he found that the 

 oxygen absorbed was in the proportion of 100 

 to 81.66 of what was exhaled from the lungs. 



There is reason to believe that if physiologists 



