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The coagulation of the blood, while it is a matter of fundamental importance in physiology, has peculiar interest for the surgeon, on account of the special feature of coagulability of inflammatory exudations and the part played by lymph in the healing of wounds and various other pathological phenomena, such as the sealing of divided arteries by blood-clot. Towards the close of the investigations which I have been describing there was published another successful Astley Cooper Prize essay, "Coagulation of the Blood" having been the subject selected by the judges for the competition. The author of this dissertation, the late Dr. Richardson, propounded the new theory that the solidification of blood shed from the vessels was due to the escape of ammonia, which, as he believed, held the fibrin in solution. I was at first much struck by the evidence with which he supported this view, and my first experiments on the subject were made with a view to strengthening that evidence where it seemed to me weakest.
In one of these, a sheep having been placed under choloroform, I sought by means of a common tourniquet to constrict the thigh so extremely as to prevent the ammonia from escaping when the vessels were divided, and so keep the blood fluid in spite of amputation. Rigidity of the muscles prevented me from carrying out my intention; but I tied a bandage firmly round the foot, below the joint where the butcher removes it, so as to retain the blood, and, as far as might be, the ammonia also. The foot being severed, I took it
