xxxviii THE BLOOD. 



from the blood by the processes employed, for he believes that a portion 

 remains suspended in the liquid in form of minute microscopic scales or 

 films. 



Denis pointed out, that fibrin obtained from the coagulum of venous blood, if quite 

 recent, and not previously much exposed to the air, is capable of being slowly dis- 

 solved in a slightly-heated solution of nitre. Scherer and Nasse have confirmed this 

 statement, and the latter finds that fibrin got by stirring may also be dissolved in the 

 same way, provided it is quite fresh. On the other hand, nitre does not dissolve 

 fibrin of arterial blood, nor fibrin that has been some time exposed to the air, from 

 whatever source it may be derived; nor, according to Scherer, the fibrin of the 

 buffy coat. 



Origin of Fibrin. It is now ascertained that the fibrin is not present, as 

 such, in a liquid form, in the plasma, but is produced at the moment of 

 consolidation by the co-operation or combination of two previously distinct 

 substances. About twenty years ago, Professor Andrew Buchanan* disco- 

 vered that the fluid of hydrocele, which might in an unmixed state be 

 kept for an indefinite time without coagulating, very speedily congealed 

 and separated into clot and serum when mixed with a little blood. Ordi- 

 nary blood-serum, blood-clot, especially washed clot, and buffy coat, even 

 after being dried and long kept, when added in small proportion to the 

 hydrocele- fluid, produced the same effect. From these facts Dr. Buchanan 

 concluded that fibrin exists as a liquid both in hydrocele-fluid and in the 

 liquor sanguinis, that liquid fibrin does not coagulate spontaneously, but 

 requires for that end the influence of some " suitable re-agents," that such 

 a re-agent is naturally present in the blood, and brings about the solidifica- 

 tion of its fibrin in the natural process of coagulation, and that it is absent 

 from the hydrocele fluid, but when supplied by the addition of blood, 

 causes the fluid fibrin to solidify. On further reasoning on the facts he 

 had observed, Dr. Buchanan was led to believe that " coagulant power " 

 was mainly seated in the pale corpuscles, which abound in the washed 

 clot and the buffy coat, and are present in the serum ; and that their 

 efficacy depended on their organisation as elementary cells. In harmony 

 with this latter view, he found on trial that the organised tissues, such as 

 muscle, skin, and spinal marrow, possessed the same power, though in a 

 less degree than the pale corpuscles, in which, as primary cells, the meta- 

 bolic power is more energetic. 



The remarkable phenomenon described by Dr. Buchanan did not obtain 

 the consideration it deserved, and the coagulation of hydrocele-fluid under 

 the conditions stated, was commonly ascribed to some catalytic action of 

 the substance added, which induced liquid fibrin present in the fluid to 

 solidify. In 1861, however, Dr. A. Schmidt, of Dorpat, apparently un- 

 aware of Dr. Buchanan's observations, fell upon facts of the same kind, and 

 pursuing the investigation by an elaborate series of experiments not only 

 with hydrocele-fluid, but with pericardial, peritoneal, and other serous fluids 

 and effusions, which give a like result, has satisfactorily shown that fibrin 

 has no existence in a liquid state, but that when it appears as a coagulum 

 in a fluid, it is actually produced then and there by the union of two con- 

 stituents present in solution, and forthwith shed out as a solid matter. 

 One of these constituents, which contributes in largest measure to the pro- 



* Proceedings of the Glasgow Philosophical Society, Feb. 19, 1845. 



