BRONCHITIS. 



617 



to it. It causes the portions affected to appear as scattered, ill- 

 defined nodules of consolidation, irregular in size, and passing 

 insensibly into the surrounding tissue, which is variously 

 altered by collapse, emphysema, and congestion. These nodules 

 are of a reddish-grey colour, faintly granular or smooth, slightly 

 elevated, and soft in consistence. As they increase in size they 

 may become confluent; and in a more advanced stage they 

 become paler, drier, firmer, and to some extent resemble ordinary 

 grey hepatization. 



Microscopically examined, they are seen to consist of cellular 

 elements accumulated in the alveoli. 



The disease may, as already remarked, terminate fatally by the 



absorption of the putrescent catarrhal products, by gangrene of 



the collapsed lungs, or by sudden effusion of fluid into the 



bronchi, constituting what is termed suffocative catarrh. If a fatal 



termination does not ensue, the contents of the alveoli undergo 



degeneration, and are gradually removed, by discharge, or by 



absorption ; or, by coalescence, form caseous masses, which may 



become encapsuled, undergo the calcareous change, and thus 



become innocuous ; or may induce a diathesis favourable to 



the actual development of tubercle in the ox, and to symptoms 



Fig. 41. — Acute catarrhal pneumonia (American ox). — 

 Section through several air vesicles. Shows the alveol.ir 

 cavities filled with large granular catarrhal cells (c). (h) 

 Catarrhal cells sprouting from the alveolar waU. (a) Coagu- 

 lated mucus in which the catarrhal cells lie. — (480 diam.) 



simulating phthisis pulmonalis in the horse — that is to say, an 



