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But how was it that the blood remained fluid in other parts of the vessels? To my surprise I found that the same continued to be the case for days afterwards. And thus accident led me to recognise what I afterwards found to be the general rule, viz., that the blood, though in mammalia it coagulates soon after death in the heart and main trunks, remains fluid for an indefinite period in minor branches. The clotting in the heart had been an object of familiar observation in post-mortem examinations in the human subject, and it seems to have been assumed that the same thing occurred throughout the vascular system.
The sheep's foot, with the blood retained in its veins by a bandage applied before the animal was slaughtered, afforded the opportunity for very simple, but instructive experiments on the nature of the relations between the living vessels and their contained blood. For that the veins retained their life, even after the lapse of more than 24 hours after severance of the foot from the body, was shown by their shrinking by muscular contraction on exposure.[1]
Thus I found that a piece of glass introduced into
- ↑ As regards the ammonia theory, an experiment which proved universally convincing was this: Having exposed a vein in the sheep's foot, I pressed the blood out of it at one place, and applied liquor ammonise to the empty portion, protecting neighbouring parts of the vessel from the vapour with olive oil. After sufficient time had passed for the volatile alkali to fly off, blood was allowed to return to the part on which the caustic liquid had acted. There it soon coagulated: the very substance a mere trace of which should have kept it fluid according to the theory in question having brought about its coagulation by injuring the tissues of the living vessel.
