DISEASES OP THE BLOOD. 135 



section of a pleuro-pneumonic lung. The diseased organ 

 is consolidated^ and hence very remarkably increased in 

 weight. This depends upon extravasation of gelatinous 

 material into the interlobular areolar tissue^ whereby the 

 yellow bands of the section are produced. Lymphy 

 deposits plug up the bronchial tubes. The lobules are 

 congested, presenting a reddish-brown colour, or altered by 

 deposition of gelatinous matter in the lobular areolar 

 tissue. Sometimes the pulmonary cells have collapsed, 

 yielding to the surrounding pressure ; at other parts they 

 are filled with deposits, and are in the condition termed 

 hepatization. The bronchial lymphatic glands are en- 

 larged by gelatinous deposit. The lung in the early stage 

 presents only circumscribed hardened portions, owing their 

 solidity to gelatinous effusion (see Fig. 22). In the later 

 stages the part which is most extensively involved is gan- 

 grenous and friable, and of a greenish colour and putrid 

 odour. The diseased lungs in every case have a special 

 sickening odour. The excellency and thoroughness of 

 Professor Yeo^s work will render his summary interesting 

 to our readers, and must be an apology for its insertion : 



" 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 belong- 

 ing 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 pro- 

 ducts of chronic inflammation. 



*^ 6. The peri-bronchial lymphatics are implicated by the 

 extension of the infective process from the bronchus, and 

 are soon filled with dense exudation. 



