XXXVI INTRODUCTION 
copal, which was found to offer even stronger opposition to the passage of 
carbolic acid than oiled silk itself, and lastly, painted over both a solution 
of dextrine, which permitted the surface to be uniformly wetted. Before 
being applied to the wound this ‘protective plaster’ was dipped in a 
solution of carbolic acid. The acid was soon dissipated, and the plaster 
became an unstimulating covering to the wound, defending and _ protect- 
ing it from the direct action of the superimposed and widely overlapping 
antiseptic dressing, but in no way interfering with the outflow of the blood 
and serum. 
While these improvements in the material of the dressings and their manner 
of application were in progress, another question had been engaging Lister’s 
attention, and had been the subject of much thought and experimental inquiry. 
From an early stage he had seen that if the full advantages of the antiseptic 
system and all that it implied were to be realized in general surgical treatment, 
the method of arresting haemorrhage, and especially the kind of ligature used, 
must be reconsidered. He had very early obtained evidence that blood-clot 
could, in the absence of fermentative changes, undergo organization. In 1867+ 
he placed on record the following observation: ‘I was detaching a portion of 
the adherent crust from the surface of the vascular structure into which the 
extravasated blood beneath had been converted by the process of organization, 
when I exposed a little spherical cavity about as big as a pea, containing brown 
serum, forming a sort of pocket in the living tissues, which, when scraped with 
the edge of a knife, bled even at the very margin of the cavity. This appearance 
showed that the deeper portions of the crust itself had been converted into living 
tissue. For cavities formed during the process of aggregation, like those with clear 
liquid contents in a Gruyére cheese, occur in the grumous mass which results 
from the action of carbolic acid upon blood; and that which I had exposed had 
evidently been one of these, though its walls were now alive and vascular. Thus 
the blood which had been acted upon by carbolic acid, though greatly altered 
in physical characters, and doubtless chemically also, had not been rendered 
unsuitable for serving as pabulum for the growing elements of new tissue in its 
vicinity.’ He also made an observation which was quite novel at the time, that 
a piece of dead bone which lay exposed in the wound of a compound fracture, 
instead of being exfoliated as would have occurred in a septic wound, became 
absorbed.’ 
These and other similar observations raised the question whether ligatures 
might not be cut short and left in the wound, for it seemed reasonable to hope 
that, just as dead bits of tissue had been disposed of by absorption, so more or 
“Vol, i, p. 'S. e Vols p: 0: 
