DISEASES OF HORSES 147 



SPASM OF THE LARYNX. 



The symptoms are as follows: Sudden seizure by a violent fit 

 of coughing; the horse may reel and fall, and after a few minutes 

 recover and be as well as ever. The treatment recommended is 

 this : Three drams of bromide of potassium three times a day, dis- 

 solved in the drinking water, or give as a drench in about a half 

 pint of water for a week. Then give 1 dram of powdered nux vom- 

 ica (either on the food or shaken with water as a drench) once a 

 day for a few weeks. 



THICK WIND AND ROARING. 



Horses that are affected with a chronic disease that causes a 

 loud unnatural noise in breathing are said to have thick wind, or 

 to be roarers. This class does not include those affected with severe 

 sore throat, as in these cases the breathing is noisy only during the 

 attack of the acute disease. 



Thick wind is caused by an obstruction to the free passage of 

 the air in some part of the respiratory tract. Nasal polypi, thick- 

 ening of the membrane, pharyngeal polypi, deformed bones, par- 

 alysis of the wing of the nostril, etc., are occasional causes. The 

 noisy breathing of horses after having been idle and put to sudden 

 exertion is not due to any disease and is only temporary. Very 

 often a nervous, excitable horse will make a noise for a short time 

 when started off, generally caused by the cramped position in which 

 the head and neck are forced in order to hold him back. 



Many other causes may occasion temporary, intermitting, or 

 permanent noisy respiration, but chronic roaring is caused by par- 

 alysis of the muscles of the larynx; and almost invariably it is the 

 muscles of the left side of the larynx that are affected. In chronic 

 roaring the noise is made when the air is drawn into the lungs; and 

 only when the disease is far advanced is a sound produced when 

 the air is expelled, and even then it is not near so loud as during 

 inspiration. 



In a normal condition the muscles dilate the aperture of the 

 larynx by moving outward the cartilage and vocal cord, allowing a 

 sufficient volume of air to rush through. But when the muscles 

 are paralyzed the cartilage and vocal cord that are normally con- 

 trolled by the affected muscles lean into the tube of the larynx, so 

 that when the air rushes in it meets this obstruction and the noise 

 is produced. When the air is expelled from the lungs its very force 

 pushes the cartilage and vocal cords out, and consequently noise is 

 not produced in the expiratory act. 



The paralysis of the muscles is due to derangement of the 

 nerve that supplies them with energy. The muscles of (both sides 

 are not supplied by the same nerve ; there is a right and a left nerve, 

 each supplying its respective side. The reason why the muscles on 

 the left side are the ones usually paralyzed is owing to the differ- 

 ence in the anatomical arrangement of the nerves. The left nerve 

 is much longer and more exposed to interference than the right 

 nerve. 



