MUSCLES OF THE NECK. 375 



rounds, and is called fascia from having some development of 

 fibrous matter in its substance. 



The Sterno-Hyoideus, 



Arises thin and fleshy on the interior of the thorax from the 

 approximated surfaces of the cartilage of the first rib, the cla- 

 vicle, and the first bone of the sternum; it passes upwards some- 

 what obliquely, and is inserted into the inferior edge of the base 

 of the os hyoides. Its lower end is covered by the sterno-mas- 

 toideus. 



It draws the os hyoides towards the sternum.* 



The Sterno- Thyroideus, 



Is beneath the last, and concealed, in a considerable degree, 

 by it. It arises fleshy from the interior surface of the sternum, 

 about an inch below its upper margin, and from the cartilage of 

 the first rib; diminishing somewhat in breadth, as it ascends, it 

 Is inserted obliquely into the side of the thyroid cartilage. 



It draws this cartilage towards the sternum.t 



The Thyro-Hyoideus. 



Arises obliquely from the side of the Thyroid Cartilage ex- 

 ternally, and is inserted into a part of the base, and into nearly 

 all the cornu of the os hyoides. It seems almost like a conti- 

 nuation of the Sterno-Thyroideus, 



Its use is to approximate the os hyoides and the thyroid car- 

 tilage, in doing which it has the effect of planting the epiglottis 

 against the root of the tongue, and of drawing the cricoid and 



* Varieties* Sometimes it arises frprn the middle of the clavicle; it is double, 

 or is confounded below with the next muscle. 



t Varieties. Sometimes there are two of these muscles, one placed above the 

 other; sometimes it runs into the inferior constrictor of the pharynx; sometimes 

 it runs into the posterior margin of the thyro-hyoid muscle; sometimes the mus- 

 cle on one side is united to the other by transverse fibres. 1 have, in one in- 

 stance, Jan. 1, 1839, seen a slip at the external margin of this muscle which 

 arising from the cartilage of the first rib, ascended in front of "the great vessels' 

 and was inserted into their sheath on a level with the thyroid cartilage. 



