42 



PRACTICAL ANATOMY. 



auditory canal by rendering tense the cartilaginous parts ; and, second, to direct 

 the external ear toward a given noise. These muscles are supplied by the 

 seventh cranial nerve. 



8. Describe tlie rationale of a complete frown, 



A proper frown consists of vertical and horizontal corrugations. The verti- 

 cals are produced by the action of the corrugator supercilii on the anterior belly 

 of the occipito-frontalis muscle, acting on this so as to deflect inward its muscular 

 belly and the skin covering the same. The horizontal ridges are the result of 

 the same force, intensified to some extent by gravity. 



9. Locate the infraorbital plexus and give its formation. 



It is located one-half of an inch external to the wing of the nose. It lies 



FIG. 21. CERVICAL TRIANGLES. 



under cover of the levator labii superioris, and is formed by a communication 

 between the infraorbital branch of the fifth and the infraorbital branches of the 

 seventh nerve. 



10. Name and locate the great anastomotic blood areas on the face and tell luns 

 they are formed. 



The facial branch of the external carotid, the ophthalmic branch of the 

 internal carotid artery, the internal maxillary branch of the external carotid, and 

 the temporal branches of the external carotid are the branches of arterial trunks 

 concerned in the rich blood-supply to the face. 



Anastomotic areas : (Fig. 17) (i) The ophthalmic anastomoses with the tem- 

 poral, forming the supraorbital anastomosis, and with the angular branch of 

 the facial artery at the inner base of the orbit, forming the angular anastomosis. 

 (2) The transverse facial artery anastomoses with the masseteric branch of the 



