200 Report on the Pathological Anatomy of Fleuro-jmeumonia. 
of infective action spreading, by means of the lymph-vessels, 
from the inflamed pleura, and along the broncho-vascular 
system. But I have already stated that the pleura cannot be 
said to take the initial step in the disease, so we must look for 
some other cause of the dense opaque consolidation, which 
certainly does not depend upon pleural infection. 
The first thing that strikes one as remarkable about this form 
of lung-lesion is its shape. This always is the same as that of the 
territory supplied by the broncho-vascular system which enters 
at its deepest part. In this respect it bears some resemblance 
to the infarction. In the case of the latter, however, its mode 
of production and its cause explain its shape, but the blood 
vessels in the young cone of opaque consolidation are, as a rule, 
healthy and pervious, and tlierefore can throw no light on the 
matter. 
Let us examine what changes are constant in this cone. By 
making a fair section directly through the centre of a small 
isolated focus of the dense pale induration — and to such a stage 
of the disease we must look to learn its initial steps — three im- 
portant facts become obvious ; first, that the air-cells are filled 
with croupous exudation ; secondly, that the bronchial tube and 
its branches are plugged with a dense, adherent, fibrinous mass ; 
and thirdly, that all the lymph-vessels around these air-tubes are 
swollen and turgid, being the seat of a dense fibrinous exudation. 
Looking at such a specimen, one cannot avoid being impressed 
with the idea that the occlusion of the bronchus and the en- 
gorgement of the lymphatics immediately surrounding it must 
be the cause of the lobular consolidation and the interlobular 
exudation. The more I have tested this view by careful scrutiny 
of the diseased parts, the more firmly convinced I am of its 
truth and importance in explaining the first steps in pleuro- 
pneumonia. I am at a loss otherwise to understand the peculiar 
localisation, the sharp demarcation, and the conical shape ; all 
of which are sucli constant characters of the opaque consolida- 
tion, particularly in the early primary nodules of the disease ; 
but, if this view be correct, they are all easily accounted for. 
A focus of opaque consolidation being once established, there 
is no difficulty in accounting for the ch-ar exudation which so 
constantly surrounds it. When once the broncho-vascular set of 
lympli plexuses have become the seat of this irritating exuda- 
tion, it is easy to imagine how they will facilitate the spread of 
the disease. Encompassing the bronchus, they lead the infective 
material to irritate its coats, and cause them to undergo a kind 
of chronic destructive inflammation. At the same time, travel- 
ing along the lymphatics towards the root of the lung, . the 
inflammatory process comes upon the tributary broncho-vascular 
