130 ORGANS OF RESPIRATION. 



There are several pairs of muscles belonging to the larynx. 



1. The Thyreo-Hyoideus, as observed in the former account 

 of this muscle, looks like a continuation of the sterno-thy- 

 roideus. It arises, obliquely, from the side of the thyroid car- 

 tilage by the ridge, there; and running upwards, it is inserted 

 into a part of the base, and into nearly all the cornu of the os 

 hyoides. 



When the thyroid cartilage is fixed, it draws down the os 

 hyoides; but when the latter is fixed, it draws up the thyroid 

 cartilage. 



2. The Crico-Thyroideus arises, tendinous and fleshy, from 

 the anterior lateral surface of the cricoid cartilage, and passes 

 upwards and backwards, to be inserted into the inferior cornu 

 of the thyroid cartilage, and the adjacent part of its inferior 

 edge. 



Use, to draw these cartilages obliquely together. 



3. The Crico-Arytenoideus Posticus arises from the back of 

 the cricoid cartilage, occupying its excavation, and is inserted 

 into the posterior part of the base of the arytenoid cartilage. 



It draws the arytenoid backwards, and makes the ligaments 

 tense. 



4. The Crico-Arytenoideus Lateralis arises from the side of 

 the cricoid cartilage, and is inserted into the side of the base of 

 the arytenoid. 



Use, to draw the latter outwards, and open the chink of the 

 glottis. 



5. The Thyreo-Arytenoideus arises from the posterior face 

 of the thyroid cartilage, near its angle, and the middle crico- 

 thyroid ligament, and is inserted into the anterior edge of the 

 arytenoid cartilage. 



Use, to relax the ligaments of the glottis. 



6. The Arytenoideus Obliquus arises from the base of one 

 arytenoid cartilage, and is inserted into the tip of the other. 



