X] THE ORGANS OF LOCOMOTION 1.39 



— approximating to one another in a V-shape. Tlic respiratory 

 and vocal movements necessitate the opening and closing of the 

 angle within the V, and this is effected by the muscles of the 

 larynx. The walls of the glottis are also moved by dilator 

 (abductor) and constrictor (or adductor) muscles, and these are 

 used both in respiration and in phonation. The muscles which 

 relax the vocal cords or render them tense are exclusively 

 phonatorj' muscles. The chief changes which the larynx under- 

 goes in voice-production relate to the cords, the mouth, pharynx, 

 nasal chambers, participating in the sound produced to a greater 

 or less extent. 



Neighing in a horse is an expiratory sound, and is produced 

 partly by the mouth and the nostrils. Braying in an ass is said 

 to be partly inspirator}- and ])artly exj)iratory. Bleating and 

 bellowing (in sheep and cattle) are expirator}, the mouth par- 

 ticipating. Yawning is a deep inspiration succeeded by an 

 exjDiration. Coughing and sneezing are exclusively expiratory. 



' E/oaring ' in a horse is a diseased condition due to the paralysis 

 of one of the abductor muscles of the larynx, and almost in- 

 variably occurs on the left side onh'. 



