THE MUSCLES 71 



antibrachialis inferior, the M. pectoralis, the MM. coraco-brachialis 

 longus and brevis, the M. supra-coracoideus, and the ventral part of 

 the M. procoraco-humeralis. The dorsal and ventral groups may- 

 be further subdivided by a vertical plane into anterior and posterior 

 elements. The secondary muscles of the shoulder-girdle are the 

 MM. thoraci-scapularis, developing from the trunk myotomes 2—5, 

 the M. opercularis, which develops from the trunk myotomes 1—2, 

 and the M. cucullaris which arises from the visceral myotomes. 



2. Shoulder-muscles (PI. VII, fig. 43). 



M. opercularis (m.o.). Gaupp (1898); Kingsbury and Reed (1909). 

 Levator anguli scapulae . . . Funk (1827); Rudinger (1868) 



Mivart (1869). 

 Levator scapulae Carus (1828); Schmidt, Goddard, and van d 



Hoeven (1864); Humphry (1871); Osawa (1902) 

 Rylkoff (1924). 

 Sous-occipito-adscapulaire (32). .... Duges (1834) 



Fasciculus of protractor scapulae .... Ow^en (1866) 

 Basi-scapularis (levator scapulae) . . . Fiirbringer (1873) 



Basi-scapularis (levator scapularis) . . , Hoffmann (1873-8) 



Protracteur du scapulum (98) ..... Perrin (1899) 

 Levator scapuli ....... Driiner (1901) 



This peculiar muscle has a fleshy origin from the cartilaginous oper- 

 culum of the ear capsule. It passes directly backwards alongside the 

 dorsal trunk-muscles of the neck region, mesial to the M. cucullaris 

 and to the ninth and tenth cranial nerves, and is inserted along the 

 anterior border of the cartilaginous suprascapula. It is practically 

 circular in section at its origin, but spreads out fan-shaped at its 

 insertion. It is a derivative of the M. levator scapulae, and was first 

 named M. opercularis by Gaupp. It seems better to retain Gaupp's 

 name for the muscle in the Salamander owing to its peculiar origin 

 and function. 



Innervation : By one or two fine twigs from the first spinal nerve — 

 N. hypoglossus. 



Function : The function of this muscle is more fully discussed in the 

 section dealing with the auditory organ (p. 295), but, in addition to 

 acting as a track for auditory impulses, a tension on the muscle would 

 tend to 'damp out' the effect which would be produced by the inertia 

 of the operculum at every sudden movement of the head. For these 

 functions alone the muscle seems surprisingly powerful, but in view 

 of the lack of any direct experimental evidence it is unsafe to specu- 

 late further. 



