48 
ON THE PRESENCE AND EFFECT 
into the circulation, and hence its presence in the blood independ- 
ently of wounds or abscesses. 
In instances of idiopathic or traumatic phlebitis, the manner in 
which the pus may become mixed with the blood is obvious enough. 
There is a class of cases to which the latter appellation is commonly 
applied, which are probably not examples of inflamed veins. They 
seem rather to be of an opposite nature ; for I have seen large veins, 
which had been divided many days before death, containing puru- 
lent fluid, although their inner surfaces presented no marks of 
inflammation; and the total failure of this process in them would 
seem to have left open their wounds, so as to favour the entrance of 
pus into them from the neighbouring parts : and this consideration 
would involve an important point of practice. 
It might be asked if, on a suppurating surface, the pus-globules, 
considerably larger than those of blood, escape from the capillaries, 
how comes it that the latter particles do not escape as well? To 
which it may be answered, that the discharge of the pus-globules 
is preceded by the coagulation of the blood in these vessels; and 
that their closure, where there is a breach of continuity, is provided 
for by the formation of the clot keeping pace with its decomposi- 
tion during the suppurative process; and the blood-corpuscle, re- 
duced in size by being broken down, or by losing its external part, 
may escape, and still become enlarged out of the vessels from the 
addition of new matter, till it assumes the character of a true pus- 
globule : hence its larger and more unequal size and irregular sur- 
face than the blood-corpuscle. 
I think my experiments will render it probable that suppuration 
is a sort of proximate analysis of the blood. As the effused fibrine 
produces swelling, or is attracted to the contiguous tissue for the 
reparation of injury, the blood-corpuscles, altered by stagnation, 
become useless, and are discharged in the shape of pus, as waste 
from the system. Suppuration, therefore, would appear to be a 
physiological rather than a pathological phenomenon — pus being 
an e^crementitious discharge — a part of the blood which has become 
effete and noxious during the reparative process, whether this pro- 
cess may have been employed in limiting the extent of an abscess 
or in healing breaches of continuity. If, however, there should be 
a formation of pus in the capillaries in consequence of the stagna- 
tion and coagulation of their contents, this pus might be mixed in 
large quantities with the blood in cases where there was no declared 
suppuration, as in some of the examples brought forward in this 
paper. 
With regard to the correct observation of Muller, that the smaller 
capillaries have only the diameter of a blood- corpuscle, I shall on 
a future occasion shew, from the result of experiments, that these 
