192 ON THE COAGULATION OF THE BLOOD 
still fluid, with the exception of a crust of clot lining the wall of the vessel. 
This, gentlemen, seemed to me of itself to afford sufficient evidence that healthy 
blood has no spontaneous tendency to coagulate, requiring to be kept in check 
by an action on the part of the walls of the living vessels. This blood had 
been entirely withdrawn from the vein, and yet it remained fluid except where 
in contact with the ordinary solid. 
This conclusion has been comparatively lately strikingly confirmed by the 
experiments of more than one observer. I would especially allude to one per- 
formed by Professor Berry Haycraft.1 He has found that if a drop of blood 
is introduced, under suitable precautions, into a deep narrow jar of castor oil, 
and before the drop, which falls slowly through this oil, has reached the bottom 
of the vessel, the jar is inverted, and the drop made to retrace its steps without 
having touched the glass, this process being repeated again and again, the drop 
of blood, having never come in contact with an ordinary solid, remains fluid 
for an indefinite period. This experiment may perhaps appear to some of you 
even more conclusive than mine, inasmuch as no coagulation whatsoever occurs 
in the drop of blood under these circumstances. Certainly it seems to me that 
it confirms in an absolutely unmistakable manner the view to which I had been 
previously led. 
But there is also this interesting circumstance in Professor Haycraft’s 
observation. It had been shown amply by myself that the gases of the atmo- 
sphere are incapable of inducing coagulation of the blood; but experiments 
like those of Professor Haycraft show that the same is the case with neutral 
or chemically indifferent iguids. This seems to me to be an exceedingly inter- 
esting fact, namely, that the active living tissue, such as lines the wall of a 
healthy vessel, in its relation to the coagulation of the blood, resembles the 
mobile particles of a liquid. I say the active living tissue ; for when the living 
tissue becomes impaired in vital energy, it behaves towards the blood like an 
ordinary solid. That is the case not only when a vessel is wounded, but also 
when it is subjected to some influence which, without actually wounding it, 
is calculated to suspend or impair its vital activity. A good illustration of this 
is afforded by a fact which I have never before referred to, but which I have often 
noticed. A very valuable field for simple and instructive observations regarding 
the conditions that determine the coagulation of the blood was afforded by the 
feet of sheep, removed after the animals had been killed, the blood being retained 
in the vessels by a bandage applied below the part where the foot is removed 
* Journal of Anatomy and Physiology, vol. xxii, p. 582. 
* Dr. Freund, of Vienna, almost simultaneously and independently observed this relation of inert 
liquids to coagulation, Jahresberichte fiir Anatomie und Physiologie, 1886. 
