48 DISEASES OF THE AIR-PASSAGES. 



horse of his own, the simple operation of bleeding succeeded 

 by extensive tumefaction and suppuration of the jugular 

 vein ; and this was followed by abscess of the parotid gland, 

 disease of the larynx, and permanent roaring. 



Bands of coagulable lymph effused into and running 

 across the cavity of the windpipe constitute another source 

 of roaring ; but, I believe, a very rare one. The inflam- 

 mation is the same, and its disposition the same, as in the 

 former case ; only instead of the lymph being effused into 

 the interstices of the membrane, and thickening its sub- 

 stance [interstitial deposit , as it is called), it is poured forth 

 upon its surface, where it assumes any form chance or cir- 

 cumstances may happen to give it, and, in the end, becomes 

 organized, and part of the pipe itself, or rather of its membrane. 



In the veterinary museum formerly belonging to my 

 father is a preparation in which the muscle has been dis- 

 placed by the formation of a cross-band of coagulable lymph 

 between it and the posterior part of the tube, by which the 

 interspace is divided into two passages, one large enough to 

 admit a walnut, the other a hazel-nut. The horse it was 

 taken from breathed with labour and exertion, and, even 

 when but moderately exercised, roared aloud. 



Ossification of the larynx, by which is meant the 

 entire or partial conversion of its substance into bone, a 

 change peculiar to aged horses, may exist either as a cause 

 or a concomitant of roaring. The parts commonly found 

 thus converted are the thyroid cartilages ; though the others, 

 at a later date, may participate in the change. It seems to 

 be the result of some chronic inflammatory action excited 

 in the cartilages ; and this I ascribe to the injurious con- 

 straint to which the larynx is so repeatedly subjected, and 

 not to any of the causes which give rise to it in the mem- 

 brane. We occasionally meet with partial, but rarely with 

 entire, osseous conversion of the rings of the windpipe ; nor 

 do we often see bony accretion of them one to another. In 

 the case of the larynx, whether the ossiflcation be partial or 

 complete, the part must suffer more or less inconvenience 

 from loss of its accustomed elasticity and flexibility. 



