314 
coagulation of the blood. 
moistened by the ammonia, I put in the cork again and 
withdrew the tube. In a short time, on introducing a hook 
of fine wire into the extremity of the tube, I found the 
blood already coagulated ; but on filling off a small portion of 
the tube, I found the blood there fluid. The portion of 
blood thus exposed soon coagulated, when, a second small 
piece of the tube being removed by the file, fluid blood was 
again disclosed, which again soon coagulated; and this 
proceeding was repeated with the same results time after 
time, till, near the thick part of the tube, the ammonia in the 
blood was so strong as to prevent coagulation altogether. 
This experiment illustrates how fitted the ammonia is to 
maintain the fluidity of blood, and also how apt it is, when 
present in the blood, to fly speedily off from it, leaving it 
unimpaired in its coagulating properties; and it must be 
confessed that the end of the tube sealed with a small clot 
resembled most deceptively the extremity of a divided artery 
similarly closed. But although the experiment seems in so 
far to favour the ammonia theory, it will tell differently when 
1 mention the object with which it was performed. It ap¬ 
peared to me that, if the cause of the fluidity of the blood 
was free ammonia, then, if I provided an ammoniacal atmo¬ 
sphere in the tube, and introduced blood by pressure directly 
from the vein into this ammoniacal atmosphere, this blood, 
lying between the strong ammoniacal atmosphere on the one 
side and the ammonia naturally present in the blood, within the 
vein on the other side, ought to remain fluid ; and if it did re¬ 
main fluid, this would tend to confirm the ammonia theory, by 
making it appear that the volatile materialwas the same at both 
ends of the tube. But, to my disappointment, I invariably 
found that if I drew away the tube after a few minutes only 
had elapsed, there was already a clot in its extremity; in other 
words, the ammonia had diffused from the end of the tube 
into the blood within the vein as into a non-ammoniacal 
atmosphere. This experiment alone, if duly considered, 
would, I think, suffice to show that the blood does not con¬ 
tain enough ammonia to account for its fluidity. 
One more experiment, however, may be adduced with the 
same object. I mounted a short but wide glass tube, open 
at both ends, upon the end of a piece of strong wire, and 
connected with the latter a coil of fine silver wire, 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 
