PARALYSIS OF MUSCLES OF THE LARYNX. 443 



Moller saw similar cases, apparently of neuropathic origin, in other- 

 wise healthy horses ; Seffner in horses recovering from acute bronchitis. 

 King and Robertson referred similar attacks to ingestion of certain 

 leguminous seeds, which they consider had a specific action on the recurrent 

 nerve. Trumbower describes six cases of spasm of the larynx in horses 

 which worked together in the same field. Death occurred in a few hours. 

 Post-mortem examination showed the existence of acute laryngitis. 



When danger of suffocation is associated with these conditions, 

 tracheotomy must be resorted to at once. It is further noteworthy 

 that inspiratory dyspnoea is increased by the anxiety and unrest 

 associated with it. All excitement should, therefore, be avoided, 

 and the horse placed in a quiet, well ventilated stall. Caution must 

 be observed in the use of morphine ; doses over 8 grains often 

 cause excitement. Clysters of chloral hydrate deserve preference. 

 Preisnitz's poultices, prepared by dipping poroplastic or thick felt 

 in hot water, may be applied to the throat and neck, but must not 

 be heavy, and may sometimes be replaced by dry coverings. 



Myopathic paralysis of single muscles, or of groups of laryngeal 

 muscles, is not known in animals, but may possibly occur. Neuro- 

 pathic paralysis of the muscles of one side of the larynx (hemiplegia 

 laryngis) is, however, very frequent in horses. The greater number, 

 if not all the muscles of the larynx, which move the vocal cord are 

 supplied by the recurrent nerve. A second branch of the vagus 

 has been recognised by Exner as a motor nerve to the larynx, but it 

 has not yet been determined what influence it exerts on the function 

 of its muscles. From the construction of the larynx, as a valve 

 opening outwards, it is clear that simultaneous paralysis of the 

 constrictors and dilators must cause disturbed breathing during 

 inspiration. Should the dilators of the larynx become paralysed, 

 the arytenoid cartilages are forced towards the opening of the glottis 

 by the instreaming air, and roaring results. With a few exceptions 

 it is caused by paralysis of the recurrent nerve, and is so described 

 in the text-books, as well as in another section of the present work. 

 This paralysis is usually incurable, but the associated dyspnoea may 

 be considerably relieved by removing the passive arytenoid cartilage, 

 or by excising the lining of the laryngeal ventricle, or by tracheotomy, 

 thus providing a direct entrance for the air below the larynx. 



Roaring is also occasionally seen in other animals besides the 

 horse ; Utz and Ollmann found it in cows. Esser has described 

 paralysis of the recurrent in a dog, and Moller noted the disease in 

 two dogs. Moller also records several cases of double-sided paralysis 

 of the larynx (diplegia laryngis) in horses and dogs producing severe 

 inspiratory dyspnoea. After being walked for a short time, whistling 



