MUSCLES OF THE BODY. 14! 
65, ¢). Inner surface with the thyrohyoid (Fig. 65, f; Fig. 
67, p), the trachea (Fig. 67, 4), and the larynx. 
Actzon.—Draws the hyoid caudad. Raises the ribs and 
sternum when the hyoid is fixed. 
M. sternothyreoideus (Fig. 65, ¢’).—The sternothyroid 
lies beneath the sternohyoid and is connected with it at its 
caudal end. 
Origin from the first costal cartilage beneath the sterno- 
hyoid. : 
Insertion (Fig. 67, 0) into the lateral part of the caudal 
border of the thyroid cartilage of the larynx. 
Relations. —Outer surface with the sternohyoid (Fig. 65, ¢) 
and laterally with the sternomastoid (Fig. 65, ¢). Inner sur- 
face with the trachea (Fig. 67, 4), and at the lateral edge with 
the thyroid gland (Fig. 67, 6). 
Action.—Pulls the larynx caudad. 
M. scalenus (Fig. 73, 7/’’).—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 
(2) 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 (7). This 
ventral head passes craniad and unites with the other heads. 
