698 
COAGULATION OF THE BLOOD. 
I am aware of one source of fallacy in these experiments, 
namely, that the abdominal viscera are subject to decomposi- 
tion before the limbs ; and as soon as decomposition does set 
in, the blood coagulates in the parts which are the seat of it ; 
as, for example, in small veins of the intestines. This cause 
of error was, however, I think, guarded against in the last 
case; and considering the almost universal occurrence of 
coagulum in the heart of the human subject twenty-four 
hours after death, compared with the universal absence of it 
in the small veins of healthy parts, so far as I have yet 
examined them, both in man and in the lower animals, I 
think the fact must be admitted, that where a large mass of 
blood exists within a cavity of the heart or a blood-vessel, it 
experiences coagulation sooner than if in a small vessel of 
the same body. If- this be admitted, it becomes a strong 
argument in favour of the active operation of the tissues, for 
the blood is more exposed to the influence of the air in a 
subcutaneous vein than in the heart, and the only conceiv- 
able reason for the greater persistence of fluidity in the latter 
than in the former, is that the influence of the tissues 
operates to greater advantage upon the smaller mass of 
blood. 
Again, supposing it to be admitted that free ammonia 
exists within the blood-vessels, maintaining the fibrine in 
solution, a hypothesis which, I confess, appears to me very 
probable, — granting the ammonia theory, I say, as far as it 
can possibly be granted, it is clear that no merely neutral 
action of the tissues could check the evolution of the alkali in 
the manner described ; and nothing can tend to convince us 
more of the potency of the vital forces than to consider what 
new powers must be impressed upon the chemically inert 
constituents of the tissues, in order to enable them securely 
to chain down the alkaline gas, in spite of its excessive 
volatility. 
There is one other experiment upon the sheep’s foot which 
I do not like to omit mentioning. Having exposed a sub- 
cutaneous vein, six hours after the death of the animal, I 
pressed out the blood from an inch of it, and treated the 
empty part with caustic ammonia, the adjacent parts being 
protected with olive oil. When the smell of the ammonia 
had passed off, I let the blood return, and, two or three 
hours after, found that the portion that had had the vitality 
destroyed by the ammonia was full of clot, while the blood in 
the adjacent parts of the vein were fluid, and coagulated on 
exposure. 
This, however, was not the only result of the application of 
