72 ON SPONTANEOUS GANGRENE FROM ARTERITIS AND 
body, is a minute portion of free ammonia holding the fibrine chemically in 
solution, and that the coagulation of such blood is the result of the escape of the 
alkali. The only point on which the evidence appeared deficient was the effect 
of occlusion from air in tubes of dead matter, and this defect I endeavoured 
to supply by the experiment which I mentioned at the last meeting of the 
Society, by which I succeeded in keeping the blood of a sheep fluid for three 
hours within a vulcanized india-rubber tube, the blood coagulating in about 
two minutes when let out just as if freshly drawn from the veins of the 
animal.' Hence it appears to me that the medical profession is deeply indebted 
to Dr. Richardson for his laborious and able investigations, which have, as 
I think, removed much mystery from this long vexed question. 
But Dr. Richardson aims at much more than the explanation of coagulation 
outside the body. He believes that the fluidity of the blood within the healthy 
living vessels is due simply and solely to the presence of free ammonia, which he 
supposes to be generated either in the systemic or pulmonary capillaries, and 
he denies that the walls of the arteries or veins have any effect on the blood 
by virtue of their vitality, or exercise any other influence upon it than that of 
checking the evolution of ammonia, just as would be the case were they tubes 
of dead matter of the same degree of permeability. And all cases of coagulation 
within the living body are supposed, by him, to be explicable on simple chemical 
principles. Here, however, I find myself quite unable to follow him. Thus, 
he believes that the coagulation in an aneurysm is the result of the blood which 
is at rest in the tumour giving up its ammonia to the current which is flowing 
past the mouth of the sac. This theory was suggested to him by the following 
circumstance :—In one of the experiments of transmitting air through suc- 
cessive portions of blood, the longer tube in the last Wolfe’s bottle was 
* This experiment was performed in the following manner :—One of the jugular veins of a sheep 
having been exposed, it was emptied of blood by passing the finger along it while pressure was applied 
by an assistant at its anterior part. The vessel was then opened at two places about three inches distant 
from each other, and into each opening was tied one end of a piece of vulcanized india-rubber tube, 
a quarter of an inch in diameter, and about eighteen inches long, filled with water, to prevent the intro- 
duction of air into the circulation. The pressure was then removed from the upper part of the vein, 
so as to allow the blood to flow through the tube. It was now easy to ascertain, by observing the col- 
lapse of the lower part of the vein, when a part of the tube was momentarily obstructed by pressure, 
that the circulation was going on freely through the new channel. This having been determined, 
ligatures of waxed string were tied as tightly as possible round the tube, at intervals of about two 
inches, beginning at the end next the head and proceeding backwards, so as to avoid all tension upon 
the enclosed blood, which was, of course, displaced freely in the direction towards the thorax. By 
this means a number of portions of blood were obtained enclosed in receptacles nearly, though not 
absolutely, impermeable to gases. The various compartments were opened at different intervals, and up 
to three hours some of them contained fluid blood which coagulated on exposure, whereas there was 
in others a considerable portion of coagulum. After four hours, coagulation was almost complete, 
but a slender thread of fibrine was still obtained from the fluid part in one of the divisions a few minutes 
after it had been let out. 
