ON THE COAGULATION OF THE. BLOOD cL 
duction of any air, and then left both undisturbed. At the end of a certain 
number of minutes I found that, while the blood which had not been disturbed 
could be poured out as a fluid, with the exception of a thin layer of clot on 
the surface, and an incrustation on the interior of the vessel, the blood in the 
other vessel, which had been stirred for so brief a period, was already a solid 
mass. 
I have only lately been aware of the great influence exerted upon the blood 
by exposure for a very short time to a foreign solid, and I feel that many of my 
own experiments, and many performed by others, have been vitiated for want 
of this knowledge. Take, for example, the effect of a vacuum, which was 
observed by Sir Charles Scudamore to promote coagulation. This has been 
considered by Dr. Richardson as an illustration of his theory, the vacuum being 
supposed to act by favouring the escape of ammonia. I have lately inquired 
into this subject, and I feel no doubt whatever that the greater rapidity of 
coagulation in a vacuum depends simply on the greater disturbance of the fluid. 
I made the following experiment :—I filled three bottles, such as these, from 
the throat of a bullock, placed one of them under the small bell jar of an air- 
pump in good order and exhausted it, leaving the other two undisturbed. The 
blood happened to be slow in coagulating, and at the end of about forty minutes, 
in the vessels where the blood had been undisturbed, there was only a slight 
film of coagulum on the surface, whereas the blood under the vacuum was 
found on examination to have a very thick crust of clot upon it. But during 
the process of exhaustion the blood had bubbled very much. Indeed, any 
exhaustion of blood recently drawn which is sufficient to cause the evolution 
of its gases induces great bubbling, so that the pump cannot be used freely 
for fear of the froth overflowing. To this disturbance, involving the exposure 
of successive portions of blood in the bubbles to the sides of the vessel, I was 
inclined to attribute the more rapid coagulation; but in order to prove the 
point, I stirred for a few seconds the blood in one of the vessels hitherto undis- 
turbed. After eight minutes I emptied the three vessels. I found that that 
blood which had not been disturbed at all, either by the vacuum or by the rod, 
was still almost entirely fluid, only showing a thin crust upon the glass and 
on the surface exposed to the air. The blood which had been subjected to 
the vacuum had a thick crust of clot on the surface, and the sides of the glass 
were also thickly encrusted, but it still contained a considerable quantity of 
fluid that could be poured out from its interior. But that blood which had 
been stirred for only a few seconds was a solid mass throughout. In other 
words, gentle stirring of the blood for a few seconds had much greater effect in 
producing coagulation than the protracted and efficient exhaustion which was 
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