C 379 ] 
ting it reft till I thought the air had acquired the fame 
degree of heat as the blood, I then removed the 
intermediate ligature, and mixed the air with the 
blood. The air immediately made the blood florid, 
where in contaft with it, as could be feen through 
the coats of the vein. In a quarter of an hour I 
opened the vein, and found the blood entirely co- 
agulated: and as the blood could not in this time 
have been completely coagulated by reft alone, the 
air was probably the caufe of its coagulation. 
From comparing thefe experiments, may we not 
now venture to conclude, that the air is a ftrong 
coagulant of the blood, and that it is to this its 
coagulation when taken from the veins is chiefly 
owing, and not to cold or to reft ? 
It may not be improper to obferve here, that 
there are none of the above related experiments I 
have been obliged to repeat fo often as the 4th, which 
was made with a view to determine whether the 
blood would coagulate by reft. In the firft trial 
which I made, the vein was not opened till the end 
of three hours and a quarter ; and juft before it was 
opened I had obferved through its coats, that the 
upper part of the blood was tranfparent, owing to 
the feparation of the lymph. On letting out this 
blood, it feemed to me entirely fluid ; a part indeed 
had been loft, but the greateft part was collected in 
the cup, and which afterwards coagulated as blood 
commonly does when expofed to the air. From 
this experiment I imagined that the whole had been 
fluid j but from others made fince, I am perfuaded 
that the part which was loft had been coagulated'; 
for, from a variety of trials, 1 now find that though 
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