Report on the Pathological Anatomy of Pleuro-pneumonia. 181 
different degrees, there being usually a central focus, in which 
the pathological processes appear in a more advanced stage of 
development. 
When the lung is distended with air, so as to assume its 
normal size and shape, and give an accurate cast of the cavity 
of the chest, it becomes obvious that the diseased part is not 
only densely solid, but that it is also considerably swollen ; the 
increase in size being much more than could be brought about 
by the forcible inflation of a similar part of healthy tissue. It is 
also changed in shape, its flat surfaces having become convex, so 
that the diseased mass projects above the surface-level of the 
inflated lung as a rounded swelling, distorting the neighbouring 
lobes and pushing them from their natural position. 
If a section be made through the centre of the affected part, 
by cutting from the surface towards the root of the lung, the 
broadest side of the lesion is always at the pleural surface, 
and the narrowest points towards the root of the lung. This 
tapering off towards the entrance of the broncho-vascular system 
is very well seen in the less advanced cases, where the disease is 
localised to an area with a distinct conical outline. The base 
of this cone looks towards the pleural surface, and its apex 
inclines to the root of the lung, at which point it is found to 
correspond to the broncho-vascular system supplying this region. 
In some instances this wedge of disease is found accurately to 
correspond to one of the broncho-vascular territories which have 
already been mentioned. In the advanced stages of the disease 
this conical outline is generally lost, owing to the swelling, 
which rounds off the corners, and also to the irregular spread of 
the lesion by means of the pleura. 
The disease is often localised to one lung, the right appa- 
rently a little more frequently than the left ; but it is also often 
found in both, one generally being much more diseased than 
the other. Sometimes two or more distinct foci of morbid 
change may exist, apparently without any connection, there 
being a broad piece of healthy lung tissue between them. 
In the earlier stages of the disease, the boundary of the lesion 
of the lung is definitely marked and accurately circumscribed. 
The line of demarcation in these cases always corresponds to 
the interlobular spaces, all the lobules supplied by a certain set 
of vessels being engaged, while their immediate neighbours may 
be perfectly free. The sharp lines of demarcation, not only 
between the healthy and diseased structure, but also between 
the different territories affected with the various degrees of 
morbid change, are amongst the most striking and constant 
characters of anatomical appearances. 
Although the consolidation which is met with in this disease 
