THE THIRD HUXLEY LECTURE 539 



foot were by the constricting cord, and, like them, will act upon their contained 

 blood as if they were ordinary solids. The plasma of that blood will therefore 

 receive from the blood-corpuscles the material requisite for forming fibrine, and, 

 passing through the pores of the capillaries with that addition, will constitute 

 a coagulable exudation.^ 



On the other hand, if irritation is less severe, although the corpuscles acquire 

 more or less adhesiveness, involving corresponding obstruction to the flow 

 through the capillaries and consequent undue passage of liquor sanguinis through 

 their walls, the constituent tissues of the vessels are not reduced to the condition in 

 which they act like ordinary solids in relation to coagulation. This seems to follow 

 from the uncoagulable character of the effused fluid. For we know that what 

 used to be termed the serum of oedema or hydrocele is simply the normal plasma. 



Adhesiveness of corpuscles and coagulation are both brought about by 

 the operation of noxious agents upon the tissues of the part concerned. But 

 it by no means follows that they are in all respects analogous phenomena. We 

 have seen that normal blood has no innate tendency to coagulate, and needs 

 no action of the tissues upon it to ensure its fluidity. But the blood-corpuscles 

 may be naturally adhesive bodies, possessing a viscosity only kept in abeyance 

 by some influence exerted upon them by the living tissues in their vicinity ; 

 and such appears to be really the case. 



A very interesting observation which I made long ago, but to which I have 

 not before directed attention in this point of view, shows that an extreme degree 

 of adhesiveness of the red discs may exist within a blood-vessel, the walls of 

 which are in perfect health with reference to coagulation. If a horse's jugular 

 vein, obtained in the manner I have described, is suspended vertically, the 

 blood in it remains fluid for an indefinite period, but the red corpuscles soon 

 fall from the upper parts of the fluid, leaving a bufty layer of plasma, readily 

 seen through the translucent wall of the vessel. And this behaviour of horse's 

 blood implies, as we have seen, a high degree of adhesiveness of the red discs. 



If we compare this with the perfect absence of grouping of the red corpuscles 

 which was observed witliin a vein of the bat's wing, in spite of their extreme 

 adhesiveness in the same animal in blood shed from the bodw we cannot but 

 be greatly struck with the contrast. As regards the circumstances of the 

 two vessels, we see that in the bat's wing the vein was of small calibre, and 

 was in its natural relations to surroundinc; structures ; whereas the lunse's 

 jugular was of very large dimensions and isolated from the rest of the body. 



It seems impossible that the adhesiveness of the corpuscles in the jugular 



* I once ascertained llu- coaj^ulabilily ol a drop of clear tluiil which liad exudetl ln)m a recent 

 contused wound, by drawing tlu- point of a needle through it. to which it yielded threads of fibrine. 



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