18 Dr. Buchanan on the Coagulation of the Blood. 



frequently happens, a little blood has been accidentally mingled with 

 it, coagulation may ensue, not spontaneously, but from the re-action 

 of certain cloments of tho blood upon the dissolved fibrin. This, if 

 we leave out of sight tho propensity to make facts bend to theory, is 

 the only explanation that can be given of tho assertion frequently 

 made, but so inconsistent with observation, that the fluid of hydrocele 

 is spontaneously coagulablo. 



What are the elements of the blood that have tho power of causing 

 fibrin to coagulate ? Tho washed clot of the blood is the most efficient. 

 It is perhaps indeed the only element of tho blood that has the pro- 

 perty of coagulating fibrin. Tho washed clot is the substance which 

 is usually, but very erroneously, named the fibrin of the blood. It is 

 best obtained* by mixing one part of liquid blood with from six to ten 

 of water, and stirring them carefully for five minutes, so as to prevent 

 the blood from falling to the bottom and coagulating unmixed. After 

 the mixture has stood from twelve to twenty-four hours, it is to be 

 filtered through a coarse linen cloth, and the product washed with 

 water. The mass thus obtained consists, chiefly, of the insoluble 

 portion of the red corpuscles; next of the colourless granules and 

 globules; and least in quantity of the precipitated fibrin, by which 

 these main constituents of the coagulum are agglutinated together. 



Let a small quantity of this substance be mixed with the liquid of 

 hydrocele, reducing it to minute shreds, and diffusing it equably through 

 the liquid. Coagulation will ensue in many cases as rapidly as in the 

 liquid blood itself. The coagulum is often quite distinct in from five 

 to ten minutes. It becomes gradually firmer, and in the course of a 

 few hours admits of being passed without breaking from one vessel to 

 another, and very much resembles the transparent tremulous substanco 

 of calf- foot jelly. The power which the washed clot has of coagulating 

 fibrin is not less remarkable than that of rennet in coagulating milk, 

 to which, indeed, it may be aptly compared. This experiment is well 

 adapted to the lecture-room— the reagent being added to the liquid 

 serum at the commencement of the lecture, and the coagulated mass 

 shown at the end of it. A. very complete illustration of the process 

 by which the blood coagulates may be exhibited by adding to the 

 liquid along with the reagent some pounded charcoal, the particles of 

 which being diffused through the liquid, and getting entangled in the 

 meshes of the nascent fibrin, there is formed a black clot, which, on 

 tho addition of a little water, swims in it, just as the blood-coagulum 

 does in the liquid serum. 



The washed coagulum retains its coagulating power for a long period 

 — even after its odour indicates the commencement of the process of 

 putrefaction. In preserving it as a reagent, however, I think it ad- 

 visable to add to it a small quantity of spirits, and to keep it in a 



* Med. Gazette, lB.W. 



