76 ON SPONTANEOUS GANGRENE FROM ARTERITIS AND 
“where there is a full power of life, the vessels are capable of keeping the blood 
in a fluid state’, he also supposed that some motion, though ‘ very little, is 
required to keep up its fluidity’ (ib., p. 32). Indeed, the expression, ‘ full 
power of life,’ just quoted, is quite inconsistent with the state of a sheep’s 
foot, six days after muscular irritability has been lost. I had myself frequently 
made experiments on inflammation upon the amputated limbs of frogs, and 
observed that the blood remains fluid for more than twenty-four hours after 
death ; but muscular irritability, ciliary action, &c., also last in those creatures 
to a very much later period than in the higher animals, so that I never ven- 
tured to infer that fluidity of the blood was likely to continue long after death 
in mammalia. 
Further observations on the feet of the sheep and limbs of the cat proved 
even still more strikingly the influence of the vessels upon their contained blood. 
If the skin be reflected from over a subcutaneous vein full of blood, and lightly 
replaced, so as to protect the subjacent parts from evaporation, without exclud- 
ing the air, the vessel will be found, in two or three hours, changed from a dark 
venous colour to a scarlet arterial tint; yet no coagulation will occur in the 
blood, although the oxygen of the atmosphere has evidently penetrated freely 
through the coats of the vessel, showing that abundant opportunity has 
occurred for evolution of ammonia, provided any tendency to such an occurrence 
existed. Again, if such a vein be cut across with fine sharp scissors, without 
disturbing its connexions, or inflicting much injury on its coats, the blood 
will be found, after about six hours, perfectly fluid in the vein, up to within 
perhaps 1-20th of an inch of the wound, where a small clot is perhaps seen, utterly 
insufficient to obstruct the progress of ammoniacal vapour. Hence it appears 
to me to follow, as a matter of demonstration, that, if free ammonia really 
exists 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 depended 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 practic- 
able, 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 1—that inflamma- 
tion consists in an impairment of the vital energies of the tissues of the part 
* See p. 209 of this volume. 
