ON THE EXTERNAL CAUSES OF DISEASE. 
269 
vessel of the kind already mentioned, containing 155 centil. or 94‘5 cubic 
inches ofair. They remained there only fifteen minutes. They produced 
on an average 5 98 centil. or 3 65 cubic inches of carbonic acid, and absorbed 
1 29 centil. or 7 87 cubic inches of oxygen. Here the small si^e of the 
animals, ihe large proportion of air, the short duration of the experiment, 
the quantity of carbonic acid, scarcely any at first, and in small proportions 
at last, allow no room to doubt that the absorption was entirely at the 
expense of the oxygen, and that the same would be the case in the open 
air. 
In comparing the results of individual experiments of this kind, consider¬ 
able ditference was observable in the proportion of the oxygen absorbed to 
the carbonic acid produced, ranging between rather less than half and one 
sixth The q'.ianlity ofcarbonic acid produced was very uniform when the 
circumstances w'ere similar. Tiiis result of my experiments upon respira¬ 
tion, in regard to the great extent of variation in the proportions of oxygen 
which disappears, and of carbonic acid produced, has appeared to be im¬ 
portant, not because it reconciles the results of previous labour (though 
even that is not uninteresting), but because it establishes a fundamental fact 
of importance to the theory of that function. 
Dr. Edwards is not singular in his opinions as to the absorp¬ 
tion of azote, but is supported by Spallanzani, Humboldt, Pfaff, 
Henderson, Dulong, and last, though not least. Sir Humphry 
Davy. This chemist observed it,” says Dr. Edwards, in 
his own person in so many instances, as to leave no doubt of the 
fact.” 
Few persons have contributed more to the interests of science 
than this celebrated chemist. His name marks an epoch in the 
history of chemistry and experimental philosophy; and however 
exalted be the genius of some of his contemporaries, and nume¬ 
rous their discoveries, yet Sir H. Davy must be allowed to be the 
Newton of chemistry, and to have sustained the scientific glory 
of England during his short but illustrious career. 
His opinions on respiration coincide in great measure with those 
of Dr. Edwards. Respiration,” he says, is no more a che¬ 
mical process than the absorption of chyle ; and the changes that 
take place in the lungs, though they appear so simple, may be 
very complicated : it is as little philosophical to consider them 
as a mere combustion of carbon, as to consider the formation of 
muscle, from the arterial blood, as crystallization.” Sir Humphry 
appears to consider the changes produced by respiration upon the 
blood to be of a more important kind than is generally considered. 
Alluding to the popular theory, he says, “ I will not allow any 
facts or laws from the action of dead matter to apply to living 
VOL. VI. 
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