Page:The third Huxley lecture.pdf/55

51 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 œdema 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 he 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 he 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, hut the red corpuscles soon fall from the upper parts of the fluid, leaving a huffy layer of plasma, readily seen through the translucent wall of the vessel. And