COAGULATION OF THE BLOOD. 
315 
tube, being open at both ends, and slightly funnel-shaped at 
that end which was directed towards the heart, had thus a 
full current of arterial blood streaming through it. Having 
ascertained how long the arterial blood took to show the first 
appearance of coagulation in a watch-glass, I very soon after 
removed the apparatus, and, on taking out the coil of silver 
wire, found that it was already crusted over with coagulum. 
Yet here assuredly there had been no opportunity for the 
escape of ammonia. 
From this experiment it is obvious that there is a very 
great difference between ordinary solid matter and the living 
vessels in their relation to the blood. But the same conclu¬ 
sion may be drawn much more simply from experiments 
which 1 had the opportunity of performing after making 
an observation which it seems strange should have been left 
for me to make, and which, I may say, was made by myself 
purely accidentally; and this is, that the blood of mammalia, 
though it coagulates soon after death in the heart and the 
principal arterial and venous trunks, remains fluid for an 
indefinite period in the small vessels. If, therefore, a liga¬ 
ture be tied round the foot of a living sheep a little below the 
joint which is divided by the butcher, the foot being removed 
and taken home with the blood retained in the veins by the 
ligature, we have a ready opportunity of investigating the 
subject of coagulation, and of making observations as satis¬ 
factory as they are simple. Here are two feet provided in 
the way I have alluded to. A superficial vein in each foot 
has been exposed. The veins, I see, have contracted very 
much since I reflected the skin from them before our meet¬ 
ing ; and I may remark that such contraction, dependent on 
muscular action, may occur days after amputation, indicating 
the persistence of vital properties in the veins. Now, as I 
cut across this vein blood flows out, fluid but coagulable. 
Into the vein of this other foot has been introduced a piece 
of fine silver wire, and when I slit up the vein you will see 
the effect it has produced. Exactly as far as the silver wire 
extends, so far is there a clot in this vessel. Now, this expe¬ 
riment, very simple as it is, is of itself sufficient to prove 
the vital theory in the sense that the living vessels differ en¬ 
tirely from ordinary solids in their relation to the blood. It 
is perfectly clear that by introducing a clean piece of silver 
wire (and platinum or glass or any other substance chemi¬ 
cally inert would have had the same effect), I do not add any 
chemical material or facilitate the escape of any, and yet 
coagulation occurs round about the foreign solid. 
Again, if a blood-vessel be injured at any part, coagulation 
