146 



A MANUAL OF VETERINARY PHYSIOLOGY 



the term respiratory ^muscle might be confined to the dilator 

 of^the glottis, while the constrictors would represent the vocal 

 muscles ; but the constrictors are not entirely without a respira- 

 tory function, as, for example, in coughing, so that in the 

 following table they are included under this head. 



Dilator or abductor, 

 Constrictors or adductors of the 

 glottis, 



Respiratory Muscles. 



Crico-arytenoideus posticus. 

 Crico-arytenoideus lateralis, Ary- 



tenoideus, and Thyro - aryte- 



noideus. 



These muscles are shown in Fig. 55. 



The crico-arytenoideus lateralis and posticus are direct an- 

 tagonists ; the lateralis depresses the arytenoid cartilages and 



p IG> 55. — The Position of the Muscles of the Larynx in the Horse. 



Epiglottis ; b, opening leading to the glottis ; c, portion of the arytenoid car- 

 tilage ; d, position of the joint formed between the cricoid and arytenoid 

 cartilages ; e, the trachea. The wing of the thyroid cartilage has been 

 removed, so as to expose the constrictor muscles ; 4, 4, represents its cut 

 edge. 1 and 2, Thjnro-arytenoideus ; 1, anterior ; 2, posterior fascicules. 

 The space between these two muscles indicates the position of the ventricle 

 of the larynx. 3, Crico-arytenoideus lateralis ; 5, cricothyroid muscle, the 

 bulk of which lies inside the thyroid cartilage, and cannot, therefore, be seen ; 

 6, crico-arytenoideus posticus ; 7, portion of cricoid cartilage. The shaded 

 portion in front of the figure represents where it and the thyroid meet. 

 8, Arytenoideus muscle. 



closes the entrance into the glottis, the posticus swings 

 arytenoids upwards and outwards and enlarges the glottis. 



the 



P hortatory Muscles. 



Muscle which relaxes the vocal Thyro-arytenoideus, anterior and 



cords, especially posterior fasciculus. 



Muscle which renders the cords Crico-thyroid. 



tense, 



Muscles which bring the cords The respiratory adductors. 



together, 



Muscle which moves the cords The respiratory abductor. 



apart, 



