Dn. Bt'CHANAN on tlie Coagulation of the Blood. 17 



The experiment exhibited to tho Society, and the analogous ex- 

 periments mentioned below seem to me important, as serving to rectify 

 some prevailing opinions as to the essential properties of Fibrin, and 

 the part which it plays in the coagulation of the blood, and certain 

 other physiological processes. They are still farther interesting to 

 me, as enabling me to correct some erroneous views of tho constitution 

 of the blood which I entertained, and which having been made public 

 in the first volumo of the " Proceedings of the Society," I feel it a duty 

 to rectify. 



The opinions commonly entertained by physiologists and chemists, 

 to which allusion has just been made, are, that fibrin has a spontan- 

 eous tendency to coagulate: that this spontaneous coagulability is a 

 characteristic property of fibrin, by which it is distinguished from 

 albumen and casein: and that the coagulation of the blood, and of 

 various other animal fluids depends on the spontaneous coagulation of 

 the fibrin which they contain. My experiments, on the other hand, 

 show, that fibrin has not the least tendency to deposit itself spontan- 

 eously in the form of a coagulum: that, like albumen and casein, 

 fibrin only coagulates under the influence of suitable reagents: and 

 that the blood, and most other liquids of tho body which appear to 

 coagulate spontaneously, only do so, in consequence of their contain- 

 ing at once fibrin and substances capable of re-acting upon it, and so 

 occasioning coagulation. 



The liquid of hydrocele, and other dropsical liquids, are generally 

 regarded by physiologists as identical with, or at least closely analo- 

 gous to the " liquor sanguinis," or liquid part of the blood ; which they 

 suppose to be effused, both in health and in disease, from the capillary 

 blood vessels into the serous cavities and cellular interstices of the 

 body. I have elsewhere shown, * that of all these effused liquids that 

 of hydrocele approaches most nearly in its qualities to the serum of 

 healthy blood. In two cases in which the experiment was made, the 

 specific gravity of hydrocelic serum and of the serum of blood drawn 

 from the same individual on tho same day, differed very little ; and I 

 have recently met with an instance of hydrocelic serum drawn from a 

 very strong man having a specific gravity as high as 1-038, much 

 higher therefore than the ordinary specific gravity of the serum of 

 blood. I entertain no doubt, therefore, that the serum drawn off in 

 cases of hydrocele, is, for the most part, identical with the liquid part 

 of the blood. Such an opinion, however, can scarcely be held by those 

 who believe the liquid part of the blood to be spontaneously coagula- 

 blo ; for, without controversy, the liquid of hydrocele possesses no such 

 property, as I havo ascertained by attentive observation in many 

 hundred instances. If carefully drawn off, it may be kept till it putrifies 

 without showing tho slightest tendency to coagulate. If, again, as 



* Med. Gazette, 1186. 



Vol. II.— No. 1. 2 



