270 ROARIXG. 



Tliore can be no doubt of tlie fact, that the majority of roarers arc 

 draught-horses, and horses of quick draught. They are not only subject 

 to the usual predisposing causes of this obstruction, but there is something 

 superadded, — resulting from their habits or mode of work; — not indeed 

 necessarily resulting, but that which the folly as well as cruelty of man has 

 introduced — the system of tight-reining. To a certain extent, the curb-rein 

 is necessary. Without it there would be scarcely any command over a wilful 

 horse, and it would need a strong arm occasionally to guide even the most 

 willing. Without the curb-rein the horse would carry himself low; he 

 would go carelessly along ; he would become a stunibler ; and if he were 

 disposed at any time to run away, the strongest arm would have little 

 power to stop him : but there is no necessity for the tight rein, and for 

 the long and previous discipline to which the carriage -horse is subjected. 

 There is no necessity that the lower jaw, whether the channel is wide or 

 narrow, should be so forced on the neck, or that the larynx and the portion 

 of the windpipe immediately beneath it should be flattened, and bent, and 

 twisted, and the respiratory passage not only obstructed, but in a manner 

 closed. The mischief is usually done when the horse is young. It is 

 effected in some measure by the impatience of the animal, unused to con- 

 trol, and suffering pain. In the violent tossing of liis head he irritates the 

 larynx, and produces inflammation. The head of the riding-horse is 

 gradually brought to its proper place by the hands of the breaker, who 

 skilfully increases or relaxes the pressure, and humours and plays with 

 the mouth ; but the poor carriage -horse is confined by a rein that never 

 slackens, and his nose is bent in at the expense of the larynx and windpipe. 

 The injury is materially increased if the head is not naturally well set-on, 

 or the neck is thick or the jaws narrow. 



Connected with this is the common notion that crib-biting is a cause of 

 roai'uig. That is altogether erroneous. There is no possible connection 

 between the complaints : but one of the methods that used to be resorted 

 to in order to cure crib-biting might be a cause of roaring, namely, the 

 strap so tightly buckled round the upper part of the neck as to compress, 

 and distort, and paralyse the larynx. 



The question, however, as to the ordinary and common cause of 

 roainng remained for years an open one, but the answer has at length 

 been satisfactorily received, — the cause of roaring in the great majority 

 of cases, is a paralysis or atrophy of the muscles on the left side of the' 

 laiynx, affording, in contrast with the healthy muscles on the right side, 

 one of the most striking examples of pathological anatomy that can 

 possibly be conceived. But what is the cause of this atrophy or wast- 

 ing of the muscles, and why are the muscles thus affected always those 

 of the left side ? The cause is paralysis of the left recurrent nerve, the 

 motor nerve by which they are stiniulated to action, and this stimulus lost, 

 they, like the muscles in any other part of the body in a paralysed person, 

 lose their fullness, their colour, and their function, and become impotent 

 and flaccid. But still, why does this occur always on the left side ? The 

 reason would appear to be this — nerves in general when distributed in 

 pairs, and nearly all nerves are so, take the same course on either side 

 of the body ; the recurrent nerves, hoAvever, Avhich are the motive nerves 

 of the muscles of the larynx, are an exception to this rule, the left one has 

 a longer and more complicated route than the right : the consequence has 

 been found to be, that it is more liable to morbid change, disease, and 

 wasting than its fellow, and the muscles it ought to supply with nervous 

 energy perish away from the want of it, and cease to perform their share 

 in regulating the action of the larynx ; its opening in consequence becomes 

 distorted, and roarinu' is the result. The fureshadowino- of this was first 



