598 [June 11, 



circumstance with reference to the question which we are now con- 

 sidering, that the coagulation always begins in contact with the vein, 

 indicating that it is not the wall of the vessel that keeps the blood 

 fluid, but that, on the contrary, the wall of the vessel, when deprived 

 of vital properties, makes the blood coagulate. 



The observation of the persistent fluidity of the blood in these 

 large vessels furnished the opportunity of making a very satisfactory 

 experiment, which I hoped to have exhibited before the Society ; but 

 as there was some clot in the vein, I did not think fit to run the risk of 

 failure. The experiment is performed in the following way. A 

 piece of steel wire is wound spirally round one of the veins in its 

 turgid condition, and with a needle and thread the coats of the vessel 

 are stitched here and there to the wire, care being taken to avoid 

 puncturing the lining membrane, and thus the vessel is converted 

 into a rigid cup. Two such cups being prepared, and the lining 

 membrane of the vein being everted at the orifice of each so as to 

 avoid contact of the blood with any injured tissue, I found that, after 

 pouring blood to and fro through the air in a small stream from one 

 venous receptacle into the other half a dozen times, and closing the 

 orifice of the receptacle to prevent drying, the blood was still more or 

 less completely fluid after the lapse of eight or ten hours. On the 

 other hand, if a fine sewing-needle is pushed through the wall of an 

 unopened vessel so that its end may lie in the blood, it is found on 

 examination, after a certain time has elapsed, that the needle is sur- 

 rounded with an encrusting clot. It is scarcely necessary to point 

 out how entirely the ammonia theory and the oxygen theory, as well 

 as that of rest, fail to account for facts like these. 



While the blood may remain fluid for forty-eight hours in the 

 jugular vein of a horse or an ox, it coagulates soon after death in the 

 heart of very small animals, such as mice ; so that it is obvious that 

 the continuance of fluidity in small vessels is not due to their small 

 size. 



It is a very curious question, "What is the cause of the blood remain- 

 ing so much longer fluid in some vessels than in others ? I believe 

 that we must accept it simply as an ultimate fact, that just as the 

 brain loses its vital properties earlier than the ganglia of the heart, 

 so the heart and principal vascular trunks lose theirs sooner than the 

 smaller vessels of the viscera, or than more superficial vessels, be they 



