INFLAMMATION OF THE LUNGS. 633 



and contagious pneumonia; that, generally speaking, the inflam- 

 mation commences in the inferior portions of the lungs ; that it 

 invades the tissue from below, upwards ; that in all cases the 

 bronchi are more or less involved in the inflammatory process ; 

 and that when the pneumonia is superficial, the pleura partici- 

 pates in the inflammatory process, losing its normal colour and 

 translucence, becoming opaque, and covered with a layer of 

 fibrinous material ; that the exudation, whether it be into the 

 parenchyma or on the surface, is fibrinous. When the disease 

 originates deeply within the lung substance, the pleurisy may 

 be and occasionally is absent. 



Wlien the pulmonary inflariamation terminates in resolution, 

 or a gradual return of the lung to its normal condition — and this 

 termination is the most frequent one in ordinary pneumonia, 

 provided the animal be properly treated — the exudates liquefy, 

 undergo fatty degeneration and disintegration, and become so 

 altered that they can be removed by absorption, and as the 

 softened matters become absorbed, the circulation is gradually 

 restored, and the lung slowly attains its normal character. 



In glanderous pneumonia, the exuded materials are trans- 

 formed into an ichorous, infecting, puriforrn fluid, and in pleuro- 

 pneumonia-bovina contagiosa they undergo a caseous necrotic 

 change ; the inflammatory process meanwhile continuing in 

 other portions of the lungs until a large part of them becomes 

 consolidated, impervious to air, and the animal dies from suffo- 

 cation and aniemia. 



The various stages of pneumonia are manifested by certain 

 sounds detectable by the ear when applied to the sides of the 

 chest. In the first stage, and previous to the occurrence of much 

 engorgement, a crackling sound is heard, mingling with the 

 vesicular murmur, over the inflamed part ; the sound is of the 

 smallest and finest kind of crepitation, similar to that emitted 

 by salt when thrown on hot coals. As the inflammation ad- 

 vances the crepitations become more and more pronounced, until 

 they entirely supersede the vesicular murmur. These crepitations 

 do not remain long; they are superseded either by a return of the 

 vesicular murmur, indicating the resolution of the inflammation 

 by a tubular sound, or an entire absence of sound. — (See 

 Auscultation.) 



