1863.] 



595 



Fig. 5. 



One more experiment, however, may be adduced 

 with the same object. I mounted a short but wide 

 glass tube, open at both ends (T, fig. 5), upon the 

 end of a piece of strong wire, W, and connected 

 with the latter a coil of fine silver wire, S, so that it 

 hung freely in the tube. I then opened the carotid 

 artery of a horse, and through the wound instantly 

 thrust in the apparatus so far that I was sure 

 the tube lay in the common carotid, which in 

 veterinary language means the enormous trunk 

 common to both sides of the neck of the animal. 

 The tube being open at both ends, and slightly 

 funnel-shaped at that end which was directed 

 towards the heart, had thus a full current of 

 arterial blood streaming through it. Having 

 ascertained how long the arterial blood took to 

 show the first appearance of coagulation in a watch- 

 glass, I very soon after removed the apparatus, 

 and, on taking out the coil of silver wire, found that 

 it was already crusted over with coagulum. Yet 

 here assuredly there had been no opportunity for 

 the escape of ammonia. 



From this experiment it is obvious that there is a very great dif- 

 ference between ordinary solid matter and the living vessels in their 

 relation to the blood. But the same conclusion may be drawn much 

 more simply from experiments which I had the opportunity of 

 performing after making an observation which it seems strange 

 should have been left for me to make, and which, I may say, was 

 made by myself purely accidentally ; and this is, that the blood of 

 mammalia, although it coagulates soon after death in the heart and 

 the principal arterial and venous trunks, remains fluid for an inde- 

 finite period in the small vessels. If, therefore, a ligature be tied 

 round the foot of a living sheep a little below the joint which is 

 divided by the butcher, the foot being removed and taken home with 

 the blood retained in the veins by the ligature, we have a ready 

 opportunity of investigating the subject of coagulation, and of making 

 observations as satisfactory as they are simple. Here are two feet 

 provided in the way I have alluded to. A superficial vein in each 



