AND ITS RELATIONS TO THE LIVING ORGANISM. 275 



fine needle) transversely through an adjacent artery and vein of a dog, and 

 left it there, so that it might cut the stream, for a period of from twelve to 

 twenty-four hours; the consequence of which was, that a coagulum was formed 

 upon the thread more or less completely obstructing the vessel. There was, 

 however, a marked difference in the coagula formed within the artery and 

 the vein respectively, which may be attributed to the difference in the quality 

 of the fibrin in the blood of the two vessels, or to the difference in the rate 

 of its motion, or to both causes conjointly ; for the thread which traversed 

 the artery usually presented a " vegetation " on its surface, sometimes as 

 large as a grain of wheat, always of a pyramidal shape, with its base attached 

 to the thread, and its apex down stream ; whilst the venous coagulum was 

 a voluminous black clot, chiefly collected on that side of the thread remotest 

 from the heart. 1 



210. Again, the contact of dead animal matter with the Blood appears to 

 promote the coagulation of its fibrin in a very remarkable degree, occasion- 

 ing coagula to form, whilst it is yet actively moving in the vessels of the 

 living body. Thus M. Dupuy found that the injection of cerebral substance 

 into the veins of an animal occasioned its death almost as instantaneously 

 as if prussic acid had been administered ; the circulation being rapidly brought 

 to a stand, by the formation of voluminous clots in the heart and large ves- 

 sels. These experiments were repeated and confirmed by M. de Blaiuville. 2 

 The same effect is produced with still more potency, when the substance in- 

 jected is rather undergoing degradation, than actually dead ; for it then seems 

 to act somewhat after the manner of a ferment, producing a marked dimi- 

 nution in the vitality of the solids and fluids with which it may be brought 

 in contact. Such is pre-eminently the case with pus, as was long ago observed 

 by Hunter, and as Mr. H. Lee has since determined more precisely. It was 

 found by the latter, that healthy blood received into a cup containing some 

 offensive pus coagulated in two minutes ; whilst another sample of the same 

 blood, received into a clean vessel of similar size and shape, required fifteen 

 minutes for its complete coagulation. When he injected putrid pus into the 

 jugular vein of a living ass, coagulation took place so instantaneously as to 

 produce an immediate obstruction to the current of blood, so that the vessel 

 at once acquired a cord-like character ; and in this mode, the pus was usually 

 prevented from finding its way into the general current of the circulation. 

 Whilst it thus remains circumscribed by a coagulum of blood, the pus so 

 introduced seems to produce no other constitutional disturbance than is at- 

 tributable to the local injury; but if the circumscription should be incom- 

 plete, and the pus should be carried into the general circulation, it becomes 

 a source of extensive mischief, determining the formation of abscesses in 

 various parts, and producing a most depressing influence on the system at 



1 Lectures on General Pathology, p. 56. Mr. Simon applies this fact to the expla- 

 nation of the " vegetations " which so commonly present themselves upon the valves 

 of the heart, in cases of rheumatic endocarditis; maintaining that they are simple 

 deposits from the fibrin of the blood, which is unusually abundant in this condition. 

 This doctrine can only be substantiated, however, by a careful microscopic examina- 

 tion of these substances ; and if they should be proved to have the simple constitution, 

 which Mr. Simon imputes to them, the fact will in no degree set aside (as he seems 

 to consider it must do) the existence of endocardia! inflammation, but will rather 

 confirm it, since the deposition of fibrin on those particular spots is likely to be spe- 

 cially determined by inflammation of the subjacent membrane. 



2 Gazette Medicale, 1834, p. 521. There is no reason to suppose that cerebral sub- 

 stance possesses a more special influence than would be exerted by any other tissue 

 which could be as easily mixed up with the circulating current. The presence of a 

 piece of flesh or of the clot of blood, as Prof. Buchanan has shown, often suffices to 

 determine the coagulation of fibrin in a solution from which it would not otherwise 

 have separated. 



