596 [June 11, 



foot has been exposed. The veins I see have contracted very much 

 since I reflected the skin from them before our meeting ; and I may 

 remark that such contraction, dependent on muscular action, may 

 occur days after amputation, indicating the persistence of vital pro- 

 perties in the veins. Now as I cut across this vein, blood flows out, 

 fluid but coagulable. Into the vein of this other foot "has been intro- 

 duced a piece of fine silver wire, and when I slit up the vein you will see 

 the effect it has produced. Exactly as far as the silver wire extends, 

 so far is there a clot in this vessel. Now this experiment, very simple 

 as it is, is of itself sufficient to prove the vital theory in the sense 

 that the living vessels differ entirely from ordinary solids in their 

 relation to the blood. It is perfectly clear that by introducing a 

 clean piece of silver wire (and platinum or glass or any other sub- 

 stance chemically inert would have had the same effect) I do not add 

 any chemical material or facilitate the escape of any, and yet coagu- 

 lation occurs round about the foreign solid. 



Again, if a blood-vessel be injured at any part, coagulation will 

 occur at the seat of injury. As a good illustration of this, and also 

 as bearing upon the ammonia theory, I may mention the following 

 experiment. Having squeezed the blood out of a limited portion of 

 one of the veins of a sheep's foot, and prevented its return by appro- 

 priate means, I treated the empty portion with caustic ammonia, the 

 neighbouring parts of the vein being protected from the irritating 

 vapour by lint steeped in olive oil. After the smell of ammonia had 

 passed off, I let the blood flow back again and left it undisturbed for 

 a while, when I found on examination a cylindrieal clot in the part 

 that had been treated with ammonia, while in the adjacent parts of 

 the same vessel the blood remained fluid. I repeated this experi- 

 ment several times and always with the same result. Where the 

 ammonia had acted there was a clot. The chemical agent used here 

 was one which, so long as any of it remained, would keep the blood 

 fluid ; yet its ultimate effect was to induce coagulation, the vital pro- 

 perties of the vein having been destroyed by it. 



If a needle or a piece of silver wire is introduced for a short time 

 into one of the veins of the sheep's foot, it is found on withdraw alto 

 be covered over with a very thin crust of fibrin, whereas the wall of 

 the vessel itself is never found to have fibrin or coagulum adhering 

 to it unless it has been injured. Now this seems to imply that the 



