THE RESPIRATORY APPARATUS. 325 



into the interlobular tissue, so that in an acute case the 

 lungs have a sodden appearance. 



III. Interstitial ^-nieumonia or lung induration is a 

 chronic form consisting in hyperplasia of the interlobular 

 areolar tissue, due to persistence of disease in this struc- 

 ture after the more acute attack in the other lung elements 

 has subsided. It results in diminution in size of the air- 

 vesicles which undergo atrophy, in great firmness of lung 

 tissue, and extensive emphysema. Sometimes it is an 

 effect of broncho-pneumonia, in other cases of pleuritis. 



There can be no doubt that each of these forms of pneu- 

 monia occurs in the ox. The croupous or exudative form 

 in pleuro-pneumonia zymotica, in which its exudative and 

 lobar characters are well marked and the mottled state of 

 the section is very evident. The catarrhal form results from 

 exposure, alternations of temperature, and other like causes 

 to those which originate bronchitis. Sometimes it depends 

 on the entry of acrid medicines and solid particles into the 

 lungs, as seen when the protective influence of laryngeal 

 sensibility is interfered with, as in parturient apoplexy, or 

 when the pneumogastrics have been injured. Besides the 

 ordinary signs of fever we find that there is a suppressed 

 cough, and the animal generally lies, but sometimes stands 

 with the muzzle protruded. The extremities are of variable 

 temperature until the latter stages, when they are persist- 

 ently cold. The pulse is frequent, and afterwards becomes 

 rapid, small, and weak. The breathing is accompanied by 

 a grunt, and is even, short, and quick. Ausculation shows 

 at first crepitus, but the vesicular murmur is soon lost ; 

 percussion gives a dull sound. As the disease progresses 

 suppuration or gangrene may supervene. The former 

 result is rare, except when due to specific disorder, as the 

 impactment of emboli in the blood-vessels. It is indi- 

 cated by rapidly increasing debility, a peculiar resonance 

 of the cough, and the cavernous rale. Also a purulent 

 discharge passes up from the lungs and sometimes this 

 contains the debris of the disorganised tissue. When gan- 

 grene takes place, there is a rapid sinking of the patient, 

 sudden fall of temperature, coldness of the extremities, and 



