RESPIRATORY APPARATUS. 123 



in paralysis of the arytenoid cartilages the instrument can be 

 used to advantage. [This instrument, which is a modified 

 endoscope, consists of a cylinder 56cm long and 4.7cm in diam- 

 eter, at one end of which is an optical illuminating apparatus. 

 The light is furnished by an electric battery, and undue heat 

 is prevented by a special cooling arrangement. The instrument 

 is inserted through the nostrils and can be used in the horse 

 without casting.] In left-sided paralysis of the larynx (roar- 

 ing) the left arytenoid cartilage is seen to project farther into 

 the lumen of the organ than the right one. This can be more 

 distinctly seen when the larynx is moving. As the larynx of 

 the horse is usually held in the position of "middle inspiration," 

 it is necessary to induce forced inspiration and expiration. To 

 do this the thorax is encircled with a girth which is slowly 

 and gently drawn tight and relaxed, alternately, imitating 

 forced breathing. The larynx in the meantime is watched 

 through the instrument. At each inspiration the healthy car- 

 tilage is seen to move outwardly, while at each expiration it 

 approaches the middle line. The diseased cartilage, on the 

 other hand, either remains completely at rest (paralysis) or its 

 movements are very tardily performed (paresis). 



In bilateral paralysis (paraplegia) of the larynx the 

 patient may show dyspnea when at rest — at any rate, slight 

 excitement will induce it. In such cases one will note that 

 both arytenoids protrude into the lumen of the larynx at inspi- 

 ration ; at expiration they are suddenly forced laterally and set 

 in vibration. The paralysis can be complete or incomplete; 

 it may not be developed to the same degree on both sides. 



Palpation. When we determine the seat of the en- 

 largements by palpation we may at the same time note 

 their temperature, sensitiveness, and the ease with which 

 cough can be induced by pressing upon them. Where much 

 exudation is found in the larynx, infiltration of the yocal cords 

 or other folds of mucous membrane, a trembling of the organ 

 may be felt (laryngeal fremitus). 



