610 SPORADIC DISEASES. 



The mudo-purulent material thus incarcerated is driven or 

 impacted by the ramrod-like action of the inspirated air into 

 the periphery of the smaller tubes and vesicles, and there con- 

 stitutes those masses which may undergo putrefaction in the 

 horse, causing septicemia, as already explained, and caseous 

 masses, mistaken for tubercle in the ox. 



The physical signs of bronchitis are as follows : — Percussion 

 returns a more or less resonant sound, but auscultation will enable 

 the practitioner to detect the nature and extent of the bronchial 

 inflammation. FJionchus, confined to the upper and middle 

 third of the chest, with true respiratory murmur over the lower 

 part, will indicate inflammation of the larger and middle 

 sized bronchial tubes, and a condition of comparatively little 

 danger. Sihilus, heard at the lower parts, indicates a condition 

 of much greater danger, and that the disease involves the 

 smaller tubes and air vesicles. Inspiration is generally short- 

 ened, expiration prolonged, and more distinctly accompanied by 

 the abnormal sounds. These sounds are succeeded at a later 

 stage by moist bubbles, rattles, or rales — mucous rales. At first 

 the discharge expelled by coughing is thick, tenacious, and gela- 

 tinous, or watery and scant. The lower animals do not, however, 

 expectorate in the true sense of the word ; some discharge issues 

 from the nose, but the greater part of what is coughed up falls 

 into the fauces, and is swallowed. As the disease advances, 

 however, a profuse discharge issues from the nostrils, and the 

 inflammation gradually subsides. The cough becomes less 

 hoarse, more vigorous, and even more frequent than at first ; but 

 it gradually disappears, the discharge becomes again thinner, 

 clearer, and eventually ceases. 



In some instances all sounds disappear from a certain part of 

 the lungs. This is due to occlusion of the tubes and vesicles 

 by the catarrhal secretion, or to more or less collapse of the 

 vesicular tissue, dependent on obstruction to the passage of air 

 during inspiration by glutinous or inspissated mucus. This 

 coUapse is often confined to individual lobules, which are thus 

 condensed, heavy, indurated, and of a dark colour, and may 

 ultimately become hepatized, atrophied, or even emphysematous. 



