62 



THE MUSfiLES. 



16. M. masseter (Figs. 56, 57 m). 

 Duges, zygomato-maxillaire, n. 29. 



Arises as a somewhat broad muscle from the horizontal process of 



the quadrato-jugal and is inserted 

 into the outer side of the lower 

 jaw, opposite the insertion of the 

 m. temporal is. 



Fig- 57- 

 t 



lid. 



dm 



Muscles of the lower jaw of Rana esculenta, 

 dm M. depressor maxillae cut through and 



reflected. 



La M. levator anguli scapulae. 

 l.d. M. latiss. dorsi,cut through and reflected. 

 m M. masseter. 

 pt M. pterygoideus. 

 t Scapula. 

 *' Suprascapula. 

 t.c. M. sternocleidomastoidens. 

 1 1 M. temporalis cut through and reflected. 



*' 17. M. svlii/axit/aris (Figs. 58, 

 59, 6 1 ism, sm'}. 



Cuvier, in. mylo-hyoidens, I.e., II, 

 536. Zenker, un/ln-sternoideux, 

 p. 25. Duges, sous-maxillaire, n. 

 15- 



This muscle forms the floor of 

 the mouth as does the mylo- 

 hyoidevs in man; it is, however, 

 not inserted into the hyoid bone. 



It arises- i. From the whole of 

 the inner surface of the upper 

 border of the lower jaw 1 , except 

 near the angle (Fig. 58 SID) ; 



2. By a small portion (Figs. 58, 

 59, 6 1 smf) near the skull, from 

 the cartilaginous anterior cornu of the hyoid-bone which projects 

 from the cartilaginous part of the prootic bone. This portion 

 descends along the cornu to unite with the other portion. The 

 two together form a membranous layer, the fibres of which run 

 transversely and meet in a band of connective tissue along the 

 middle line, forming a kind of linea alba. The sheath runs for- 

 wards to the most projecting part of the lower jaw superficially to 

 the m. sulmenfalis. Slightly in front of its posterior border the 

 muscle is attached in its whole breadth to the skin of the throat 

 by a fine lamella of connective tissue, which is not always complete. 

 The posterior border of the muscle is attached to a fascia, which 

 passes between the deeper muscles and is attached to these. It is 

 known that this muscle plays an important part in the movements 

 of respiration and swallowing; but its precise action has not yet 

 been worked out. 



1 A second origin from the lower border of the mandible, described by Klein, is 

 not to be found. The appearance is due to the exit of vessels and nerves from the 

 groove between the mandible and the muscle. 



