DISSECTING MANUAL. 



uous with and entering into the carotid sheaths, form com- 

 partments; a layer enclosing the infrahyoid muscles runs in 

 front of the trachea to the hyoid bone; another runs in front 

 of the trachea and encloses the hyoid body; another runs 

 between the trachea and oesophagus; another (prevertebral 

 layer) runs between the prevertebral muscles and the pharynx 

 and oesophagus. [400] 



MUSCLES. 



Platysma Myoides (a thin quadrilateral sheet). Origin; 

 clavicle; pectoral deep fascia. Insertion; (anterior fibres) op- 

 posite Platysma; (middle fibres) lower border of mandible, 

 Depressor labii inferioris, Depressor anguli oris; (posterior 

 fibres) Risorius. [401] 



Muscles of Face. 



Orbicularis Palpebrarum. This transversely oval sphincter 

 occupies the eyelids and is divisible into an external portion, 

 whose coarse fibres spread onto the forehead, temple, and 

 cheek ; and an internal portion whose finer fibres lie in the eye- 

 lids under the skin. It is attached internally to the inner 

 tarsal ligament and the borders of the naso-lachrymal groove. 

 The fibres in the margin of each lid form a separate ciliary 

 bundle. The posterior fibres running from the posterior edge 

 of the naso-lachrymal groove to the tarsal ligaments behind the 

 lachrymal sac form the Tensor tarsi. [402] 



Corrugator Supercilii. Origin; nasal eminence. Insertion; 

 Orbicularis palpebrarum. [403] 



Pyramidalis Nasi. Origin; Occipito-frontalis; skin over the 

 glabella. Insertion; a membrane covering the nose. [403] 



Compressor Naris. Origin; superior maxilla. Insertion; a 

 membrane covering the nose. [403] 



Dilatores Naris. These are two weak slips, one in front 

 and one behind, on the outer side of the edge of the 

 nostril. [403] 



[60] 



