1863.] 597 



ordinary solid is the active agent with reference to coagulation that 

 it is not that the blood is maintained fluid by any action of the living 

 vessels, but that it is induced to coagulate by an attractive agency on 

 the part of the foreign solid. We see at any rate that the foreign 

 solid has an attraction for fibrin which the wall of the vessel has 

 not. 



And yet I own I was at first inclined to think that the blood- 

 vessels must in some way actively prevent coagulation. There were 

 two considerations that led to this view. One was, that the blood 

 remained fluid in the small vessels after death, but coagulated in 

 the large. Now why should that be ? It seemed only susceptible of 

 explanation from there being some connexion between the size of the 

 vessel and the circumstance of coagulation. It looked as if in the 

 small veins the action of the wall of the vessel was able to control 

 the blood and keep it fluid, but that the large mass in the principal 

 trunks could not be so kept under control. The other circumstance 

 was, the rapid coagulation of a large quantity of blood shed into a 

 basin. Why should this occur unless there was some spontaneous 

 tendency in the blood to coagulate? It seemed scarcely credible 

 that it was the result of contact with the surface of the basin. 



Both these notions, however, have since been swept away. In the 

 first place, I have observed recently that it is by no means only in small 

 vessels that the blood remains fluid after death. If blood be retained 

 within the jugular vein of a horse or ox by the application of ligatures, 

 either before or after the animal has been struck with the poleaxe, it 

 will often continue fluid, but coagulable, in that vessel, which is up- 

 wards of an inch in diameter, for twenty-four or even forty-eight hours 

 after it has been removed from the body. I say often, but not always. 

 The jugular vein seems to be in that intermediate condition, between 

 the heart and the small vessels, in which it is uncertain whether it will 

 retain its vital properties for many hours, or will lose them in the 

 course of one hour or so. Unfortunately for my present purpose, it 

 happens that in this jugular vein, removed from an ox six hours ago, 

 coagulation has already commenced, as I can ascertain by squeezing 

 the vessel between my fingers. But now that I lay open the vessel, 

 you observe that the chief mass of its contained blood is still fluid, 

 and we shall at all events have an opportunity of seeing that what is 

 now fluid will in a short time be coagulated. It is an interesting 



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