10 Roaring in Horses. 



professor, Dupiiy, in the same year to perform experiments 

 on horses, in which, after dividing or compressing the vagus 

 or recurrent nerves, he constantly produced the pecuhar 

 roaring sound; and after the death of these animals the 

 laryngeal muscles were found wasted. The explanation he 

 gave of the phenomenon was to the effect, that as the 

 inferior laryngeal nerves which supply the dilator muscles 

 of the glottis are branches of the par vagum, of course these 

 muscles become paralyzed Avhen the nerves are divided or 

 compressed ; but the superior laryngeal nerves, being dis- 

 tributed to the constrictor muscles of the larynx, and not 

 being implicated in the experiment, these muscles retain 

 their power, and their antagonists — the dilators — being 

 paralyzed, the glottis is nearly closed — hence the roaring.^ 



This, though not altogether a correct explanation, marked 

 progress in the right direction. 



In 1834, Professor F. Giinther, then director of the 

 Hanover Veterinary School, asserted that Roaring is due to 

 wasting of the muscles on the left side of the larynx, owing 

 to loss of function of the recurrent nerve of that side ; as 

 since January, 1830, he had found that division of this 

 nerve produced the sound in breathing, as well as the 

 before-mentioned morbid changes in the muscles of that 

 side.2 



The observers of those days, however, did not overlook 

 the fact that various causes would give rise to noise in 

 breathing, and these causes are mentioned. 



Percivall, our highest veterinary authority in England 

 during the first half of the century, when he published his 

 lectures in 1824, showed that the observations of Godine 

 and Bouley had attracted his attention. He thought, so 

 far as the larynx is concerned, that Roaring in young 

 horses is due to thickeninof, with occasional ulceration, of 

 the laryngeal mucous membrane ; he mentions bands of 

 lymph across the larynx and windpipe, ossification or dis- 



i " Rccueil de Med. Yeterinaire," 1826. ^ Op. clt. 



