ON THE FUNCTIONS OF LIFE. 867 



and sometimes die in convulsions, as if suffocated 

 by mephitic gases. That the above symptoms are 

 greatly augmented by exertion, is evident from 

 the fact, that aeronauts have ascended equally 

 high with much less inconvenience, while sitting 

 tranquilly in their cars. When on the 15th of 

 September 1804, Gay Lussac rose in a balloon 

 to the height of 23,040 feet above the sea, his 

 respiration was hurried, his pulse frequent, his 

 hands benumbed, and his body chilled through- 

 out. And it was found by Lavoisier, that Guinea 

 pigs could live in air that contained only one- 

 third its usual proportion of oxygen, when the 

 carbonic acid was absorbed by pure potass, but 

 not without torpor and drowsiness. It is there- 

 fore probable, that men might exist at an eleva- 

 tion of 30,000 feet, with warm clothing, while at 

 rest, better than at 15,000 feet in a state of exer- 

 tion ; for we have seen that above three times 

 more oxygen is required during active muscular 

 motion, than in a state of repose. 



It was long ago observed by Dr. Halley, that 

 life was supported longer in the condensed air of 

 a diving bell, than on the surface of the earth. 

 And the younger Brunei found that on going out 

 of a diving bell, thirty feet under water, he could 

 remain twice as long without inspiration, as in 

 the ordinary state of the atmosphere. After 

 commenting on this fact, Dr. Faraday states, 

 that on taking a few deep inspirations, he could 

 refrain from breathing much longer than usual. 



