CHAPTER XVII 



AFFECTIONS OF THE RESPIRATORY AND CIRCULATORY 

 SYSTEMS 



The horse suffers from quite a number of respiratory 

 troubles ; in fact, it seems to be somewhat predisposed 

 to complaints of this kind, some of which are of a 

 " chronic " nature, others " acute/' Any portion of the 

 respiratory system (see Anatomical Outlines of the 

 Horse) is liable to be affected, but the commonest trouble 

 of all is that implicating the upper portion of the great 

 air tube, the larynx, and popularly known as *' roaring.'* 



This last-named affection occurs to all classes of 

 horses and mules, and it is customary to regard its 

 existence in any horse as a sufficient reason for rejecting 

 the animal on the ground of unsoundness. It is not always 

 due to a laryngeal affection, but in quite 90 per cent of 

 instances it is due to degenerative changes in certain 

 muscles of the larynx. 



The trouble is usually progressive and permanent, 

 but sometimes this abnormal sound is only temporary as 

 sometimes occurs in strangles and lead poisoning, likewise 

 through the consumption of the Indian vetch. Some 

 horses, instead of making a roaring sound whilst at work, 

 make a whistling noise — the animal being known as a 

 *' whistler." 



Both these sounds vary in their intensity according to 

 the duration of the disease and with the degree of exertion 

 the animal is compelled to undergo. 



It is an unfortunate matter for the horse that the 

 disease is so common. Some of the finest thoroughbreds 



164 



