TE CAUSES OF COAGULATION OF THE BLOOD Ta 
affected, I resolved to destroy the vitality of a vein, and then permit the blood 
to flow through it for some time, and ascertain whether coagulation would 
occur in spite of the current, as it must do in phlebitis... The agent which 
seemed best adapted for inflicting the lesion was strongest liquor ammoniae, 
both on account of its rapid action, and also from the circumstance that, as 
Dr. Richardson has shown, its chemical effect upon the blood, whether applied 
concentrated or diluted, is to prevent coagulation. On the 8th inst., having 
exposed one of the jugular veins of a sheep, and isolated it from surrounding 
connexions for six inches of its length, carefully avoiding even momentary 
obstruction of the flow through it, I placed a plate of glass beneath the vein, 
to protect the neighbouring tissues from the action of the alkali, and at 3! 13™ 
p.m. emptied the portion of vein of its blood, by stroking the finger along 
it, while an assistant exerted gentle pressure on the anterior part, and then at 
once applied the liquor ammoniae thoroughly, with a camel’s hair brush, to all 
sides of the vessel throughout the length exposed. The application of ammonia 
occupied three-quarters of a minute, and three-quarters of a minute later the 
blood was again allowed to flow through the vessel, having been arrested 
altogether a minute and three-quarters. A short time having been allowed 
for the evaporation of the ammonia, the edges of the wound were brought 
together with stitches. At 4» 58™, or an hour and three-quarters later, the 
wound having been opened, the flow was again obstructed as before, and the 
vein was rapidly sht up. A small amount of dark coagulum escaped with the 
fluid blood. The interior of the vessel was now immediately examined. A valve 
with three flaps, about the middle of the opened portion, was rendered con- 
spicuous from the fact that a black coagulum existed between each of the flaps 
and the wall of the vessel; and on careful observation of the lining membrane 
of the vein in other parts, it was seen to be dotted over in patches with fine 
granular deposits of pink fibrine, which could only be detached by firmly scrap- 
ing with the edge of the knife, reminding me precisely of the close adhesion 
of the clot which occurred in the popliteal artery in the case which I related 
at the commencement of this paper, and which is known to be characteristic 
both of arteritis and phlebitis. Here it is clear that the coats of the vessel 
having been deprived of their vitality, the blood flowing through it assumed 
* Sir Astley Cooper performed experiments to show the effect of mechanical injury of the coats 
of a vein upon the coagulation of the blood at rest within a portion of the vessel contained between 
two ligatures; and he came to the general conclusion, that loss of vitality in the vessel greatly ac- 
celerated the process of coagulation. Dr. Richardson alludes to these experiments, but says they have 
been invalidated by subsequent investigations by Scudamore. I have not as yet seen Sir Astley’s own 
account of his researches on the subject, but, from a notice of them by Palmer, in his edition of Hunter’s 
works, I suspect that they do not deserve to be set aside so lightly. 
