39 



during inspiration. It is much louder than whisthng, but is not of such a 

 shrill character. In most instances, and of these we shall first speak — 

 roaring is a chronic disease due to wasting and consequent paralysis of 

 certain muscles of the larynx, or upper part of the windpipe ; but it may also 

 be one of the signs of active inflammation of the larynx itself, in which 

 case it is merely temporary, and does not constitute permanent unsoundness. 



The origin of the wasting of these particular muscles is not certainly 

 known, but we may mention that it more usually attacks those of the left 

 side only, though it may sometimes involve those of the right side, and that 

 it frequently ends in the paralysis of the muscles themselves. Now, as the 

 muscles which open the larynx are those which become paralysed and 

 unable to act, when the horse takes an inspiration, the characteristic sound 

 called roaring is emitted. Roaring is in most instances gradually developed. 

 At first the sound may be intermittent, and even weeks may elapse before it 

 recurs after being once heard. As the muscles continue to waste, there is a 

 corresponding and permanent loss of power or paralysis, and what at first 

 was intermittent becomes established. In most instances, however, the 

 noise is not intermittent, but gradually increases in proportion to the waste 

 and paralysis of the muscles. The roarer generally emits a very characteristic 

 cough in addition to the abnormal sound, and this cough is loud, deep, 

 harsh, and dry. Most roarers, moreover, are liable to grunt in addition. 



Hereditary influence plays a very prominent part in the transmission of 

 roaring, and Professor Williams mentions a breed of horses in which nearly- 

 all the animals of both sexes are roarers. Horses and geldings are, however, 

 more likely to become roarers than mares, which are but rarely so afflicted. 

 Small ponies are rarely, if ever, affected with roaring. It has been noticed 

 that animals predisposed to roaring in most cases suffer from inflammation 

 of the throat from very slight causes, and the disease usually manifests 

 itself after several such attacks of sore throat and cold. The long-continued 

 use of a tight bearing-rein may induce this complaint, by distorting the 

 natural shape of the larynx. Roaring may also be due to tumours or other 

 diseases of the nose, or to tumours in the chest cavity, or to injuries or 

 distortions of the main air tube, or trachea, as it is termed, or finally to any 

 distortion or narrowing of the larynx itself. 



It is said that in India roaring is almost unknown among horses bred 

 there, in spite of the fact that many of their imported sires have been 

 confirmed roarers, and that this complaint is equally as rare among Arab as 

 among Indian horses. Horses also at the Cape are said to be but rarely 

 affected. In what direction are we to seek for the explanation of this 

 comparative immunity enjoyed by horses in these particular localities.^ 

 There can be but little doubt that the influence at work is more probably 

 climatic than dietetic, though both factors may each play their part. There 

 is good reason to suppose that hay given in too large amount, especially 

 when containing a large proportion of rye grass, is an exciting cause of 

 roaring. Cart-horses, moreover, fed on large quantities of dry, hard straw 

 .and chaff, are probably also rendered more prone to this wasting paralysis ; 



