COAGULATION OF THE BLOOD. 
457 
“ But if the ammonia theory fails to explain the coagulation 
that occurs in aneurism, still more inadequate does it appear 
to account for the phenomenon in arteritis or phlebitis. How 
can the fact that the wall of the vessel is inflamed determine, 
on simply chemical principles, the evolution of ammonia 
from the blood within it? Being convinced that in these 
and other cases of coagulation of the blood in local diseases 
of the vessels something remained quite unexplained, 1 have, 
during the last fortnight, made several experiments, with a 
view to throwing further light upon the subject, and will now 
communicate to the Societ} T the results at which I have arrived. 
“In reflecting upon the matter, some circumstances in 
physiology and pathology appeared to me to indicate that, on 
the hypothesis that the blood does contain free ammonia in 
the living body, the healthy vessels must have a special power 
of preventing its escape. Thus, the blood in the capillaries 
of the lungs is separated from the air in the air-cells only by 
an excessively thin partition of permeable living tissue; yet 
Dr. Richardson’s experiments have shown that there are 
times in the day, as, for instance, early morning, in which 
not a trace of ammonia is given off in the breath. Again, in 
surgical emphysema, the tissues of the body may be enor- 
mously distended with air, without any special tendency to 
coagulation of the blood in the vessels, such as might be 
anticipated, unless their parietes had a special power of pre- 
venting the escape of ammonia. It is true that in this case, 
the blood being in constant circulation, a perpetual supply 
of lost ammonia might be maintained by the capillaries; but 
it occurred to me that some information might perhaps be 
gained upon the point in question, by producing emphysema 
artificially in a limb in which the circulation had been arrested. 
For this purpose I applied a tourniquet firmly to one of the 
fore legs of a sheep, just above the elbow, and then injected 
air, by means of a condensing syringe, into the tissues of the 
lower part of the limb. The struggling of the animal, how- 
ever, caused repeated displacement of the tourniquet, which 
I did not succeed in retaining in position for longer than an 
hour at a time. But, though the experiment was so far a 
failure, it yielded fruit in an unexpected manner. Having 
amputated the limb and preserved it, though with little ex- 
pectation of learning anything from it, 1 was surprised to 
find, on examining it six hours later, that, although the 
cellular tissue about the vessels was still fully distended with 
air, the blood within them was perfectly fluid, and coagulated 
in about two and a half minutes, when shed into a saucer. 
Still greater was my surprise on finding next day, sixteen 
hours after the amputation, that the blood was still fluid in 
