Pathology and Course of Chronic Roaring. 101 



the arytenoid cartilage, and its taking an oblique direction 

 inwards, the supra-glottic cavity is asymmetrical in shape, 

 and, instead of being oval, has become comma-shaped, and 

 therefore greatly diminished in size. The processus vocalis 

 of the cartilage, as well as the vocal cord attached to it (and 

 which is now flaccid), share in the depression to a corre- 

 sponding degree ; not only so, but they are much nearer the 

 middle line of the cavity than those of the right side. As 

 a result of this, the pars vocalis, and to some extent the 

 pars respiratoria, is narrower than we find it in the healthy 

 larynx : showing that, even after death, if the dilator 

 muscles are not wasted, they still possess sufficient tension 

 to prevent the arytsenoid cartilages falling so deeply into the 

 cavity of the larynx, as when they are weak or atrophied. 

 As a rule, the lining membrane and vocal cords are healthy, 

 and the cartilages themselves may or may not be ossified ; 

 but this is quite independent of Roaring. 



These are the principal alterations found on the left side of 

 the larynges of horses which have been affected with chronic 

 Roaring to a serious degree. In all the autopsies which I 

 have made of such horses, I have never found any other 

 changes, strange to say ; while Professor Goubaux, of the 

 Alfort Veterinary School, has dissected sixty-five horses 

 which had been Roarers, and Leblanc, of Paris, sixty-one, 

 and both have found all the larynges affected with left- 

 sided muscular atrophy. I have already mentioned that 

 GUnther was of opinion that this uni-lateral atrophy is 

 the cause of 96 per cent, of the cases of Roaring, and 

 I am inclined to place it still higher. 



When the muscles of the rio-ht side are also involved 

 (bi-lateral paralj^sis), very few cases of which are recorded as 

 occurring in the horse, then the atrophy is said to be not 

 so marked in them. 



In very rare instances, there is found disease of one or more 

 of the cartilages (perichondritis), contraction of the whole 

 laryngeal cavity (due to inflammatory processes in the 



