MUSCLES OF THE BODY. 141 



65,^). Inner surface with the thyrohyoid (Fig. 65,/; Fig. 

 6y y p), the trachea (Fig. 6y , 4), and the larynx. 



Action. — Draws the hyoid caudad. Raises the ribs and 

 sternum when the hyoid is fixed. 



M. sternothyreoideus (Fig. 65, g-'). — The sternothyroid 

 hes beneath the sternohyoid and is connected with it at its 

 caudal end. 



Origin fi-om the first costal cartilage beneath the sterno- 

 hyoid. 



Insertion (Fig. 6"/, o) into the lateral part of the caudal 

 border of the thyroid cartilage of the larynx. 



Relations. — Outer surface with the sternohyoid (Fig. 65, e~) 

 and laterally with the sternomastoid (Fig. 65, g). Inner sur- 

 face with the trachea (Fig. 6"] , 4), and at the lateral edge with 

 the thyroid gland (Fig. 6"] , g). 



Action. — Pulls the larynx caudad. 



M. scalenus (Fig. 7l,f-f"'). — This is a large and com- 

 plex muscle lying on the ventral side of the neck and the 

 lateral surface of the thorax. It might equally well be classified 

 with the muscles of the thorax. It is divisible into a consider- 

 able number of interconnected bundles which are sometimes 

 described as separate muscles. 



The largest, middle portion (scalenus medius) (/') takes 

 origin by thin tendons from the sixth, seventh, eighth, and 

 ninth ribs, just dorsad of their junction with the cartilages; 

 these tendons unite near their origins to form a flat band which 

 becomes fleshy at about the fifth rib, passes craniad, and unites 

 just craniad of the first rib with the other parts of the muscle. 

 The dorsal portion (scalenus posterior) (/") has origin by a 

 very slender tendon from about the middle of the outer surface 

 of the third or fourth rib ; it extends craniad as a narrow band 

 which passes laterad between the heads of the serratus anterior 

 (z) that are attached to the second and third (or third and 

 fourth) ribs, and unites with the other heads. The ventral 

 head (part of scalenus anterior) (/'") arises by one or two 

 minute tendons from the cartilages of the second and third ribs ; 

 they are partly united with the transversus costarum (y ). This 

 ventral head passes craniad and unites with the other heads. 



