365 
.AND OPERATIONS DPON LIVING ANIMALS. 
antidotes, are perhaps, or at least were, more allowable than any 
others ; but the discovery of the stomach-pump is of more value 
than all that ever have or could have been made. And yet, so dif- 
,ferently do poisons act on different animals, that no observation 
drawn from their action can be applied to man. Hemlock, as every 
o;ie knows, is a wholesome food for the goat, but it poisoned So¬ 
crates; while, on the other hand, a dog will be destroyed by a 
quantity of mix vomica which a man can swallow with impunity. 
Coi'rosive siihlimate is fatal to the dog, even in a small quantity, 
but to horned cattle it may be given in a very large dose, with 
impunity. Arsenic may be given to the horse in a dose of the 
eighth of an ounce, and, in veterinary medicine, is a valuable 
tonic. Even these are experiments cruelly made, and from which 
no practical or useful knowledge can be gained. 
ON THE EXTERNAL CAUSES OF DISEASE. 
[Aerial Poisons, See. &c. continued from page 270.] 
By Mr. W. F. Karkeek, F.5'., Truro. 
We concluded our last paper with stating, that the forma¬ 
tion of carbonic acid gas does not take place wholly in the 
lungs, but by the immediate union of the oxygen of the atmo¬ 
sphere with the carbon contained in the venous blood all over 
the body.’’ 
A great difference of opinion has existed for some time on 
this part of our subject. 
We have already produced sufficient proof of the absorption 
of oxygen into the system. That carbonic acid is exhaled is ad¬ 
mitted by every one ; and it is likewise almost generally admitted, 
that whatever be the oxygen abstracted, the quantity of carbonic 
acid formed is nearly, if not altogether, an equivalent; for the 
same causes which affect tTie consumption of oxygen have an 
equal influence upon the formation of carbonic acid gas. 
But this cannot be the only source of carbonic acid gas contained 
in the blood, as it has been shewn by Dr. Edwards, Davy, and 
others, that certain species of animals can exhale in a given time 
as much carbonic acid in hydrogen as in atmospheric air. There 
must be, consequently, some other source whence it is de¬ 
rived. Gurine, Chevreul, Magendie, and others have proved by 
their researches, that this gas exists in almost the whole extent 
of the alimentary canal. It must be evident, then, that it is 
formed in the process of digestion. It is calculated by Professor 
Brand*, that two cubic inches ok this gas are contained in every 
* Philosopliical Transactions. 
3 A 
VOL. VI. 
