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THE VETERINARIAN, APRIL l, 1834. 
Ne quid falsi dicere aiidoat, ne quid veri non audeat.— Cicero. 
ON THE EXTERNAL CAUSES OF DISEASE. 
[Aerial Poisons, &e. &c. continued from p. 559 vol. vi.] 
lly Mr. W. F. Kahkeek, V. S., Truro . 
In the preceding numbers of Tue Veterinarian, when 
considering the phenomena of respiration, and its effects on the 
animal economy, we stated, that it was not to be considered as a 
purely chemical process,—a simple combustion in the lungs, in 
which the oxygen of the inspired air united with the carbon of 
the blood to form carbonic acid, to be expelled from the system; 
but a function composed of several acts; having on the one hand, 
absorption and exhalation, attributes of all living beings; on the 
other, the intervention of the two constituents of the atmosphere, 
oxygen and azote . 
If we for a moment consider the properties of vegetable and 
animal life, we must acknowledge it far beyond our comprehen¬ 
sion. The lowest stage of vitality and irritability appears to carry 
us beyond mechanism,—beyond chemical affinity. 
For this view of the subject we were indebted to Dr. Edwards, 
Sir Humphrey Davy, and others, whose opinions are not the 
offspring of speculation, but the necessary result which they 
were led to by a multitude of facts. It exhibits to us animated 
beings drawing from the composition of the atmosphere two of 
their constituent principles, since not only is oxygen conveyed 
into the mass of the blood, but azote likewise*". 
These opinions, we shewed, were strongly supported by Sir 
E. Home’s miscroscopic discovery of the anatomical structure of 
the lungs, which proves beyond a doubt, that they are calculated 
to receive supplies from the atmosphere, and to carry a part of 
„ them, with the greatest facility, to the heart. 
But an additional interest belongs to the subject when we 
view the atmosphere as connected with the vital principle; for, 
on investigation, we shall discover, that if the air has an admix¬ 
ture of certain principles, the vitality of all living bodies is in- 
I- r * * f . — 
I • ' ' I 
* Dr. Edwards on the Influence of Physical Agents. 
VOL. Vll. F f 
