ROARING IN A HORSE. 
487 
The horse had been bought, from an advertisement in the 
Times , as the property of a <£ gentleman leaving town who, 
unfortunately for my client, never returned. It was therefore 
impossible to recover its value, and the purchaser was anxious 
to avoid a total loss. We talked the matter over together; 
I explained the pathology of roaring, and he suggested the 
operation of tracheotomy, which, however, in spite of pro- 
fessional enthusiasm, was abandoned, in deference to the 
opinion of the Society for the Prevention of Cruelty to 
Animals, who, whatever comfort the horse might have derived 
at our hands, would scarcely have consented to its being 
worked in London with a perforation in the windpipe. 
The discussion, however, caused me to reflect upon 
the matter, and it became my opinion that temporary 
relief, at least, might be obtained by mechanical means. 
It would be superfluous to tell your professional readers, 
that the most general cause of “ roaring” is atrophy of the 
muscles, which should dilate the glottal opening, and a conse- 
quent falling in of one or both the arytenoid cartilages, when 
vibrations during excited inspiration produce the sounds ; or 
to mention that, when the horse is at rest, the air passes into 
and out of the lungs so quietly, that, even upon auscultating 
the region of the larynx, no sound can be heard. Such is the 
accepted theory. Indeed it is not until the respiration has 
been increased either by the excitement of the whip or exer- 
cise, that the noise becomes audible. 
Taking this view of the pathology of “roaring,” there is a 
perfect analogy between the respiratory apparatus of a horse 
labouring under the disease, and an ordinary toy trumpet, 
which sounds by the vibrations of the reed within it. If the 
reed of such a trumpet be tolerably stiff, you may blow gently 
through it without producing any sound, the current of air 
being insufficient to call forth its vibrations. Blow harder, 
and the trumpet speaks. If, however, the velocity and 
volume of air be much increased, the reed is compressed 
against the sides of the tube, its vibrations cease, and the 
tube becomes impervious to the further passage of the wind. 
Carrying out the comparison: the external nostrils of the 
horse form the mouth of the trumpet, the arytenoid cartilages 
become the speaker or reed, and the trachea a continuation 
of the tube of the instrument. 
When respiration is tranquil, the current of air passing 
through the glottal opening is not enough to agitate the car- 
tilages, we therefore hear no sound ; but frighten the horse 
with a whip, or increase the respiration by exertion, and the 
roaring commences. Should both sides of the larynx be 
