350 veterinary surgical Operations 



Williams' Operation Against Roaring in Horses 



DEFINITION. — A resection of the mucous membrane 

 lining the vocal ventricle with the object of fixing the vapid 

 arytenoid cartilage with cicatricial tissue. 



INDICATIONS. — The operation is indicated for roaring 

 due to laryngeal hemiplegia regardless of the severity of the 

 affliction. Roaring of this variety exists in all degrees of 

 severity and in horses of all ages after having passed the pe- 

 riod of colthood. It is seldom seen in yearlings, is rare in 

 two-year-olds but thereafter it is a common affliction. The 

 operation is most successful in adults whose laryngeal and 

 tracheal cartilages are less susceptible to harmful inflamma- 

 tions provoked by the operation than younger subjects. The 

 operation should be avoided under the age of five years, be- 

 fore which age it should only be performed as an emergency. 



The 'role played by the vapid arytenoid cartilage in the 

 causation of roaring is that of being drawn into the laryngeal 

 lumen by the air current. Normally, during inspiration, the 

 arytenoids are drawn apart by the crico-arytenoideus posti- 

 cus muscles ; that is to say, the space between them is wid- 

 ened at each inspiratory act. In the forcible inspirations re- 

 quired to supply air during exertion, they are drawn widely 

 apart ; in fact they are forcibly imbedded into the soft struct- 

 ures around them, leaving the laryngeal opening free from 

 any obstruction. When the motor nerve governing these 

 movements is paralyzed and the muscles upon which the 

 movements depend are atrophied as a consequence of the 

 paralysis, the left arytenoid cartilage hangs limp and helpless 

 against the air current, and is drawn inward by the air in- 

 stead of being drawn outward by the muscles during each act 

 of inspiration. Its movements are passive. Generally, how- 

 ever ,the paralysis is only partial; the muscles are only enfee- 

 bled, and the cartilage moves faintly, although not sufficiently 

 to counteract the forcible air currents required to supply the 

 lungs during severe exertion. Roaring may be lucidly de- 

 picted as a constant combat between the air current and the 

 enfeebled crico-arytenoideus posticus. When the air current 

 is gentle, as in ordinary respiration, the strength of the mus- 

 cle is sufficient to prevent roaring, but as soon as the balance 

 of power is against the muscle, the cartilage flips into the 

 lumen of the larynx and audible noise is at once produced. 



With these facts in mind the object of surgical interven- 

 tion is plain ; the flipping of the cartilage before the air cur- 



