CHRONIC DISEASES OF THE LARYNX. 471 



the chance of this, but have recourse at once to tracheotomy. 

 When this has been accompUshed we ought to allow the tube 

 to remain in the trachea until the laryngeal complications 

 have perfectly subsided. 



II. Chronic Diseases of the Larynx. 



The chief chronic diseases of the larynx which attract atten- 

 tion in the horse, viz. muscular atrophy and degeneration, 

 with the existence of adventitious growths and changes of in- 

 herent tissue, have already been noticed when speaking of 

 abnormal laryngeal sounds classed as ' roaring.' 



CHAPTER XYIII. 



DISEASES OF THE LUNGS — PNEUMONICL 



General Observations. — In observing disease of the pulmonary 

 structures as presented to our consideration in the living 

 animal, we find that active inflammatory action is to some 

 extent mapped out and distinguished by the character of the 

 tissues invaded, as well as the symptoms attending it. The 

 structures mainly concerned in the making up of the lung- 

 substance, the great respiratory bellows, are (1) The great 

 air-tubes or conduits, bronchial tubes which pass on and are 

 distributed to all parts of the lung-substance, terminating 

 in (2) The air-ceUs or sacs, ^:»76^77ionar?/ air-cells or 'paren- 

 chyma of the lungs ; and (3) The expanded sheet-like mem- 

 brane covering this structure proper, the pulmonary pleura — 

 this pulmonary pleura, or visceral pleura, forming part of that 

 serous sac interposed between the lungs and the thoracic walls, 

 the portion intimately associated with the latter being known 

 as the costal plev^ra. 



In the actual occurrence of inflammatory action and its 

 results, one or more of these separate structures may be in- 

 volved and exhibit s3Tnptoms diagnostic of its more severe or 

 more extensive involvement than the others. When the air- 

 tubes, great or small, are the special seat of inflammatory 



