100 Roaring in Horses. 



recognisable as muscles; but their antagonists upon the 

 other side were unusually red and strong. Now, these 

 muscles, contracting in pairs, are all employed in dilating 

 (sic) the glottis; but if one set act by themselves, this orifice 

 is not only distorted, but actually diminished in dimension, 

 in consequence of the arytsenoid of the opposite side being 

 drawn over it. Thus it is, then, that Roaring is produced." 

 But the cause of these changes were beyond his comprehen- 

 sion, and the conjectures of others he deemed unworthy of 

 comment. 



The alterations in the larynx of a horse which had been 

 a Roarer to a severe degree for some time, is singularly 

 striking when compared with a healthy larynx, and its 

 appearance is shown in the frontispiece to this work. The 

 horse from which this larynx was obtained was known to 

 have suffered for a long time from Roaring, and was greatly 

 distressed when much exerted. It will be seen that the 

 left dilator muscle (posterior crico- arytsenoid) has dis- 

 appeared, its place being occupied by some fat and connec- 

 tive tissue, and that the arytenoid cartilage which that 

 muscle elevates in inspiration is lower than its fellow ; while 

 the arytsenoideus muscle above it has only a few fibres of 

 muscular tissue left. The epiglottis, in consequence of the 

 depression of the arytajnoid cartilage, is slightly inclined to 

 the left side. The dilator, as well as the arytaBuoideus 

 muscle, on the right side, is healthy, and even more 

 developed than in an unaffected larynx. The other muscles 

 on the left side offered the same appearance of degeneration 

 as the arytsenoideus, with the exception of the crico- 

 thyroideus, which was quite healthy and plump : this 

 muscle, it will be remembered, being supplied with motor 

 filaments by the spinal accessory nerve, the wasted muscles 

 by the inferior laryngeal or recurrent nerve. 



The deformity in the larynx, due to this wasting of the 

 muscles on its left side, is perhaps still more apparent if we 

 look into its cavity. In consequence of the depression of 



