204 Report on the Pathological Anatomy of Pleuro-pneumonia. 
To recapitulate, then, the various items in the pathological 
sequence may be thus enumerated : 
1. Irritation of the mucous membrane of the smaller bronchi, 
probably by some infective material (specific virus ?). 
2. Chronic ulcerative bronchitis, localised to a few minute 
bronchi. 
3. Occlusion of the affected air-tubes. 
4. This produces such changes in the air-cells belonging to 
the affected tubes that the lobular parenchyma becomes solid. 
5. As the bronchial disease progresses, the walls of the air- 
tubes become thickened and infiltrated with the products of 
chronic inflammation. 
(i. The peribronchial lymphatics are implicated by the ex- 
tension of the infective process from the bronchus, and are soon 
filled with dense exudation. 
7. The block in the lymphatics of the broncho-vascular system 
impedes the flow of lymph from the corresponding territory. 
8. The tributary lymph-channels are thus mechanically 
engorged, and at the same time they are irritated by infective 
materials. 
9. The inflammation of all the coats of the air-tube gradually 
spreads towards the root of the lung. 
Thus we have a deep-seated cone of typical consolidation, 
traversed by numerous wide whitish lines, corresponding to the 
swollen interlobular connective tissue (marbling). In fact, the 
essential features of the disease are all established. 
The morbid process seldom stops here, however. It spreads 
in two ways. 
First, by the broncho-vascular lymph-passages : — 
1. The irritating and infective materials find their way along 
the lymphatics towaids the root of the lung, following the 
normal course of the lymph stream. 
2. The wall of the bronchus becomes affected after a time by 
the irritative matter in its surrounding lymphatics. 
3. The lymphatics of tributary bronchial tubes, met with as 
the disease thus advances, are choked, and the drainage of their 
territory impeded. 
4. The interlobular lymph spaces of the newly affected 
territory soon become filled with exudation. Thus the clear 
kind of consolidation is produced. 
Secondly, by the pleura : — 
1. The pleura becomes affected over the focus of consoli- 
dation by means of the subjacent lymphatics. 
2. The pleurisy soon extends far beyond this limited region, 
or the serous membrane becomes generally inflamed. 
