Page:The third Huxley lecture.pdf/48

44 home, and, having raised a portion of the skin so as to expose a subcutaneous vein, I investigated the state of the blood in it. I found it indeed fluid, with one exception, full of significance, though I did not see its import at the time, viz., where the cord used by the butcher for tying the feet together had pinched the veins against the bone, there, and there only, was* the blood in them coagulated. I remember being a little disappointed, as well as puzzled by that appearance. It was not in harmony with the theory in which I was at the time disposed to believe. And yet how replete were the facts with possible instruction! Compression of the veins had certainly given no opportunity for escape of ammonia. It is equally certain that the cord did not make the blood coagulate by any direct action upon it: for the cord, so long as it remained in position, kept the parts of the veins which it compressed empty of blood. It is clear that the effect was due to the action of the cord upon the walls of the vessels. Not that it had wounded them, nor is there any reason to suppose that it had killed them. No doubt if the animal had been released instead of slaughtered, the veins would in due time have recovered. But the mechanical violence which the hard round cord exerted, being pretty severe and long continued, had prostrated for the time the vital energies of the tissues on which it had acted; and we had, in coagulation of the blood, a repetition of the class of phenomena we had studied in the blood-corpuscles.