^8 THE MUSCLES. 



inserted into the whole extent of the upper eyelid, especially 

 near the caudal angle. Here the fibres unite with those of the 

 orbicularis oculi {c). 



This muscle is continuous caudad with the intermedins 

 scutulorum {a), craniad with the orbicularis oculi (c); laterad 

 with the corrugator supercilii lateralis {d). Toward the medial 

 side the fibres lose themselves in a tendinous sheet that joins 

 the galea aponeurotica. 



Relations. — Outer surface with the integument. Inner sur- 

 face with the frontoscutularis and the skull. 



Action. — Raises the upper eyelid. 



M. orbicularis oculi (Fig. 63, c\ Fig. 64, s). — This con- 

 sists of two thin bands of muscle-fibres which lie one in either 

 eyelid parallel to its border and unite at the angle of the eye. 



Origin by short tendon-fibres from a tubercle on the surface 

 of the frontal process of the maxillary bone just dorsad of the 

 orbital end of the lachrymal canal and between the two parts 

 of the quadratus labii superioris (Fig. 63, / and q). 



The muscle splits into two parts which pass into the two 

 eyelids. At the outer angle of the eye the two bands unite 

 by the intervention of tendon-fibres between the muscle-fibre 

 bundles of the two. 



Relations. — Outer surface with the integument. Inner sur- 

 face with the inner membrane of the eyelid. 



Action. — Closes the eye. 



M. corrugator supercilii lateralis (Fig. 63, d\ Fig. 64, k). 

 — This consists of a number of scattered fibres which arise from 

 among the fibres of the frontoscutularis, and from the tendon 

 lying just craniad of the external opening of the ear, to which 

 are united also parts of the zygomaticus (Fig. 64, d) and sub- 

 mentalis (Fig. 64, r). The fibres pass craniad, converging so 

 as to form a narrow band which is inserted at the caudolateral 

 angle of the eye, where it unites with the orbicularis oculi 

 (Fig. 64, i-). This muscle is continuous on the medial side 

 with the corrugator supercilii medialis (Fig. 64, j) and the 

 frontoauricularis, on the lateral side with the platysma. 



Relations. — Outer surface with the integument. Inner sur- 

 face with the frontal bone and the frontoscutularis. 



