THE CAUSES Or COAGUEATION OF THE BLOOD Wek 
of the blood is due to the escape of a minute quantity of ammonia, which he 
believes holds the fibrine in solution. I propose, therefore, on the present 
occasion, to consider how far this new theory accounts for this phenomenon 
of coagulation in inflammation and other diseases of the blood-vessels. 
So short a time having elapsed since the publication of the volume alluded 
to, it may be well to mention, as briefly as possible, the main facts by which 
the arguments of the author are supported :—And first I may relate the startling 
observation made by Dr. Richardson, that if a current of air is passed through 
two successive portions of freshly drawn blood, contained in two Wolfe’s bottles, 
while that in the first bottle, as might have been expected, has its coagulation 
accelerated, that in the second bottle is prevented from coagulating for several 
minutes after the time at which it would have solidified, had it been left in the 
vessel without interference. In other words, the air has had its properties so 
modified in passing through the first mass of blood, that it afterwards retards 
instead of promoting coagulation; whence Dr. Richardson infers, that it 
has obtained in its passage some volatile solvent of the fibrine. Secondly, 
Dr. Richardson has discovered that a very minute quantity of ammonia added 
to freshly drawn blood keeps it fluid for an indefinite period in a stoppered 
bottle, but that if exposed to air it coagulates as usual, though at a later period, 
in proportion to the amount of ammonia employed. He also finds that, by 
careful management, a fresh clot may be redissolved by means of ammonia, 
and that after the escape of the ammonia it will again coagulate, and afterwards 
contract in the usual manner, though more feebly. Next, he finds that ammonia 
is always to be obtained from the halitus of freshly drawn blood, and although 
the alkalinity of the blood through soda renders the ammonia excessively 
prone to escape, so that a good deal is necessarily lost from unavoidable ex- 
posure to air, yet he has succeeded in collecting about a third by weight of 
the smallest amount which he has found sufficient to keep the blood per- 
manently fluid outside the body. Lastly, he has observed that all those 
circumstances which are known to promote the coagulation of blood outside the 
body, such as an elevated temperature, free admixture with air, a vacuum, X&c., 
also hasten the process in blood mixed with ammonia, or, in other words, 
favour the escape of the volatile alkali; while, on the other hand, those things 
which check coagulation, such as cold and occlusion from air, prevent or retard 
the evolution of the gas. To the latter class he has added the remarkable fact 
that blood remains fluid for many hours under a high mercurial pressure, but 
coagulates when relieved from it. I confess that, although I was by no means 
prepossessed in favour of this theory, these facts appear to me to prove irre- 
sistibly that the cause of the fluidity of blood, after it has been drawn from the 
