508 
COAGULATION OF THE BLOOD. 
matter of demonstration, that if free ammonia reallyexists in 
the blood within the vessels, the circumstance of its being 
in those vessels deprives it entirely of its volatility ; and that, 
whether the ammonia be free in the blood or not, its chemical 
tendencies, such as it exhibits outside the body, are in some 
manner entirely modified by the vicinity of the vascular tissue. 
With regard to the nature of the modifying influence, no 
other explanation appeared to offer itself than that it de- 
pended upon residual vitality in the tissues. 
“ In order to prosecute the investigation of the cause of 
coagulation in arteritis or phlebitis, I endeavoured to produce 
artificially, as nearly as practicable, in a living animal, the 
condition in which the vessels are when inflamed. Having 
proved, as I think I may venture to say — by investigations, 
an account of which will shortly appear in the ‘ Philosophical 
Transactions' — that inflammation consists in an impairment 
of the vital energies of the tissues of the part 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 the 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 pre- 
vent coagulation. On the 8th instant, having exposed one 
of the jugular veins of a sheep, and isolated it from sur- 
rounding 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 
3T3 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 am- 
moniae thoroughly, with a camel's hair brush, to all sides of 
the vessel throughout the length exposed. 
( To be continued .) 
* Sir Astley Cooper performed experiments to show the effect of me- 
chanical 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 
accelerated the process of coagulation. Dr. Richardson alludes to these 
experiments, but says they have been invalidated by subsequent investi- 
gations by Scudamore. I have not as yet seen Sir Astley’s own account 
of his researches on this 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. 
