THE CAUSES OF COAGULATION OF THE BLOOD 7 
accidentally too short, so that it did not reach farther down than to about an 
inch from the bottom of the vessel. The result was, that while the upper part 
of the blood in this last bottle was retained fluid for a considerable time, that 
below the level to which the tube reached speedily coagulated. Dr. Richardson 
infers that the lower portion of blood gave up its ammonia to the air which 
was bubbling through the upper part sufficiently charged with the alkali to 
retain that part in a state of fluidity. But, surely, this implies a mistake in 
chemistry. The lower portion of blood coagulated, I imagine, for the same 
reasons that it would have done had it been put in a stoppered bottle’ after 
passing through the air, though probably not quite so rapidly, while the other 
part was prevented from coagulating by the ammoniacal vapour bubbling 
through it. 
But if the ammonia theory fails to explain the coagulation that occurs 
in aneurysm, 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, I have, during the last fortnight, made several experiments, 
with a view to throwing further light upon the subject, and will now com- 
municate to the Society 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 enormously distended with air, without any special 
tendency to coagulation of the blood in the vessels, such as might be antici- 
pated unless their parietes have a special power of preventing 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 from 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 
+ This occurrence I have frequently observed.—J. L. 
