THE CAUSES ,OR, COAGULATION OF THE BLOOD 75 
during the death struggle, thus exhausting their vital energies more than those 
of the other limbs. After four days, however, the blood in the hind legs, though 
still fluid, with the exception of very minute particles of coagulum, had lost 
its power of coagulation. This increasing slowness and final absence of coagula- 
tion in blood long kept within the vessels is curious, and must, I imagine, depend 
upon some gradual change in the properties of the fibrine. 
We have seen that in two classes of the higher animals, differing from one 
another as widely as the carnivora and herbivora, and after modes of death so 
various as haemorrhage, asphyxia, and an operation performed under chloroform, 
the blood remains fluid in the vessels, though perfectly at rest, for days after 
death. It may appear almost incredible that a fact of such fundamental im- 
portance, and at the same time so easy of demonstration, should have escaped 
the observation of all the eminent men who have made the coagulation of 
the blood a subject of special study; yet such appears to be the case. 
Dr. Richardson speaks of occasional instances of fluidity of the blood after 
death, and coagulation on exposure, but considers it quite essential for such 
an occurrence that the vascular system should not have been opened by wound, 
though it is difficult to see how such a circumstance could affect the question, 
according to his theory, except on the supposition that the blood-vessels were 
impermeable to gases in solution. Again, Dr. Davey, in his Researches, writes 
as follows :—‘ The blood, after death, I have often found liquid, and that many 
hours after death, when cold, but still retaining its power of coagulating’ ; 
but he had no idea of fluidity and coagulability lasting for days after death, or 
even for hours, except in rare instances. The nearest approach which I have been 
able to find to such an observation is contained in that inexhaustible treasury of 
original observation and profound reflection, the works of John Hunter, where 
the following passages occur :—‘ As a proof that blood will not coagulate in 
living vessels, in a perfect and natural state, and ready to act when powers 
were restored to it, I found that the blood of a fish, which had the actions of 
life stopped for three days, and was supposed to be dead, did not coagulate 
in the vessels, but, upon being exposed or extravasated, soon coagulated. 
. . . The blood of a lamprey-eel, which had been dead to appearance some days, 
was found fluid in the vessels, because the animal was not really dead: there 
had, however, been no motion in the blood, as the heart had ceased acting ; 
but upon its being exposed, or extravasated into water, it soon coagulated’ 
(Palmer’s edition, vol. iii, p. 32). Hunter, however, does not seem to have 
drawn any inference with regard to the higher animals from these cases. He 
speaks of ‘ the very speedy coagulation of the blood which usually takes place 
in all the vessels after death’ (vol. ili, p. 27); and though he believed that 
