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COAGULATION OF FIBRINE. 117 



dy is usually seen" in those cases, in which coagulation takes place 

 least rapidly. 



184. The conditions under which the spontaneous coagulation of 

 Fibrine takes place, are best known from the observation of that pro- 

 cess as it occurs in the Blood ; and although this fluid, as we shall here 

 after see, is of a very complex nature, yet as the Fibrine alone is con- 

 cerned in its coagulation, and as that act appears to take place in the 

 same manner as if no other substance was present, there appears to be 

 no objection to the employment of the phenomena of Blood-coagulation 

 as the basis of our account of the properties of Fibrine. There can be 

 no doubt, from Microscopical observation of the circulating Blood, that 

 Fibrine is in a state of perfect solution in the fluid ; and in this condi- 

 tion it remains, so long as it is in motion in the living body. That its 

 fluidity, however, does not depend only upon its movement, is evident 

 from two facts ; first, that no kind of motion seems effectual in pre- 

 venting the coagulation of the blood, after it has been drawn from the 

 vessels ; and second, that a state of rest within the living body does 

 not immediately produce coagulation ; a portion of blood, included be- 

 tween two ligatures in a living vessel, remaining fluid for a long time ; 

 and blood that has been reduced to a state of complete stagnation by 

 inflammatory action, being often found in a fluid state after some days. 

 On the other hand, it seems certain that the state of vitality of the 

 parts with which the blood is in contact, has a great influence in pre- 

 serving its fluidity ; thus it has been found that, if the brain and spinal 

 cord of an animal be broken down, and by this measure the vitality of 

 the body at large be lowered, clots of blood are formed in their trunks 

 within a few minutes. Nevertheless, a mass of blood effused into a 

 cavity of the living body, undergoes coagulation almost as . soon as it 

 would in a dead vessel ; but this may be accounted for by the very small 

 surface which is in contact with the blood, as compared with the mass 

 of the latter. It must be remembered that the circulating blood is con- 

 tinually being subdivided into countless streams ; and that each of these 

 passes through the living tissue, in such a manner that all its particles 

 are in close relation with the living surface. Moreover it is probable 

 that the form of matter which we term Fibrine, never remains long in 

 that condition, in the ordinary state of the system ; being continually 

 withdrawn by the nutritive processes, and as continually re-formed from 

 the Albumen, by an elaborating action hereafter to be considered. 

 Hence we may regard the state of motion through living vessels, as 

 essential to the permanent continuance of fibrine in the fluid form. 



185. The length of time, however, during which Fibrine may remain 

 uncoagulated, after it has been withdrawn from the living body, varies 

 according to various conditions ; some of which are not well understood. 

 In the first place, as already remarked, the more elaborated and more 

 concentrated the condition of the Fibrine, the more slowly does it 

 usually coagulate. Thus when a large quantity of blood is drawn, at 

 one bleeding, into several vessels, that which flows first takes the longest 

 time to coagulate, and forms the firmest clot : whilst that which is last 

 drawn coagulates most rapidly, and with the least tenacity. The coagu- 

 lation is accelerated by moderate heat, and retarded by cold ; but it is 



