CHAPTER VIII. 



INFLAMMATORY AND SUPPURATIVE CONDITIONS, 

 CONTINUED: THE ACUTE PNEUMONIAS. 



Introductory. The term Pneumonia is applied to several 

 conditions which present differences in pathological anatomy 

 and in origin. All of these, however, must be looked on as 

 varieties of inflammation in which the process is modified in 

 different ways, depending on the special structure of the lung 

 or of the parts which compose it. There is, first of all, and, in 

 adults, the commonest type, the acute croupous or lobar pneu- 

 monia, in which an inflammatory process attended by abundant 

 fibrinous exudation affects, by continuity, the entire tissue of a 

 lobe or of a large portion of the lung. It departs from the 

 course of an ordinary inflammation in that the reaction of the 

 connective tissue of the lung is relatively slight, and there is 

 usually no tendency for organisation of the inflammatory exuda- 

 tion to take place. Secondly, there is the acute catarrhal or 

 lobular pneumonia, where a catarrhal inflammatory process 

 spreads from the capillary bronchi to the air vesicles, and in 

 these a change, consisting largely of proliferation of the endo- 

 thelium of the alveoli, takes place which leads to consolidation 

 of patches of the lung tissue. Up till 1889 acute catarrhal 

 pneumonia was comparatively rare except in children. In adults 

 it was chiefly found as a secondary complication to some condi- 

 tion such as diphtheria, typhoid fever, etc. Since the recent 

 epidemics of influenza, however, it has been of much more fre- 

 quent occurrence in adults, has assumed a very fatal tendency, 

 and has presented the formerly quite unusual feature of being 

 sometimes the precursor of gangrene of the lung. Besides 

 these two definite types other forms also occur. Thus instead 

 of a fibrinous material the exudation may be of a serous or 

 haemorrhagic or of a purulent character. Cases of mixed 

 fibrinous and catarrhal pneumonia also occur, and in the 



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