98 Roaring in Horses. 



in the horse the adductor muscles of the larynx appear to 

 act primarily during swallowing, coughing, and neighing ; 

 the first is demonstrated by touching the vocal cords at their 

 junction with the arytsenoid cartilages, when there occurs a 

 regular swallowing movement, succeeded by deep inspira- 

 tion and a sharp pushing of these cartilages towards the 

 middle line of the cavity. This movement was observed 

 by Giinther some years ago, and it is a valuable criferium 

 as to the existence of paralysis ; as the cartilage on the 

 affected side remains immovable during the act. 



In this way, we also obtain at the same time an insight 

 into the act of swallowing. When it takes place the 

 entire larynx is raised, and its adductor muscles almost 

 completely close the upper compartment, while the ary- 

 epiglottic folds, as well as strong folds of the mucous mem- 

 brane of the pharyngeal cavity, cover it. This mode of 

 closure was first described by Mceller, who observed it in 

 a horse from the larynx of which both aryttenoid cartilages 

 had been removed ; and it serves to explain how swallowing 

 can be safely accomplished a few days after one or both 

 of these cartilages have been extirpated. 



Mceller has also pointed out that the epiglottis is not 

 passive during deglutition, as it is pushed over the folds of 

 mucous membrane which occlude the supra-glottic space. 

 If the hand is introduced into the pharynx, and an act of de- 

 glutition is induced by touching the larynx, the movement 

 of the epiglottis can be distinctly felt, and if attempts are 

 made to seize it, it slips away from the fingers. If the finger 

 is inserted into the larynx when the horse is drinldng, at the 

 moment of swallowing it is energetically squeezed between 

 the two aryttenoid cartilages; this movement can also be seen. 



As the result of experiment and observation on the horse, 

 then, we may accept it as a fact that the larynx is innervated 

 chiefly through the pneumogastric or vagus nerve, and in 

 such a manner that the sensory and trophical filaments are 

 supplied by the superior laryngeal nerves, and the motor 

 filaments from the spinal accessory and recurrent nerves. 



