J4 SUPERFICIAL ANATOMY OF THE HEAD AND NECK. 



ficial behind the upper part of the masseter, and from the condyle the posterior 

 margin of the raraus of the lower jaw can be followed to the angle. The lower 

 margin of the jaw can also be felt throughout, and ascending from its central point 

 the anterior edge of the masseter. Immediately in front of the latter, the facial 

 artery crosses the base of the jaw, and is readily found by its pulsation ; the course 

 of the vessel is roughly marked by a line passing upwards a little outside the corner 

 of the mouth and continued by the side of the nose to the inner canthus of the eye. 

 The coronary branch of the artery may be felt pulsating beneath the mucous 

 membrane in each lip very near its free border. Stensen's duct runs generally in 

 the direction of a line drawn from the lower margin of the concha of the ear to a 

 point midway between the ala of the nose and the free margin of the lip, but it 

 varies somewhat in position in different subjects ; accompanying the duct are the 

 transverse facial vessels (usually above) and the infraorbital branches of the facial 

 nerve (below). The interval between the ramus of the jaw and the mastoid process 

 is occupied by the parotid gland, a part of which extends forwards over the masseter 

 muscle, and the trunk of the facial nerve is deeply placed beneath the gland ; the 

 position of the nerve may be indicated by a line running downwards and forwards 

 from the anterior border of the mastoid process at the point where it meets the ear. 

 A line carried downwards over the face, crossing the supraorbital notch and the 

 interval between the two bicuspid teeth of the lower jaw, will be found to be nearly 

 vertical and to pass over the infraorbital and mental foramina, thus forming a guide 

 to the spots at which the largest cutaneous branches of the three trunks of the fifth 

 nerve come to the surface. The infraorbital foramen is about 1 cm. below the 

 margin of the orbit ; and the mental foramen is midway between the upper and lower 

 margins of the jaw. 



About the anterior half of the eyeball can be felt in the aperture of the orbit : it 

 gives a tense elastic sensation to the fingers. At the upper and inner angle of the 

 orbital opening the pulley of the superior oblique muscle may also be felt. 



When the eye is open the skin is drawn into the deep superior palpebral sulcus 

 immediately above the upper lid, and forms a loose projecting fold between this 

 furrow and the eyebrow. The corresponding inferior palpebral sulcus of the lower 

 lid is much slighter, and often broken up : it is most distinct when the eye is 

 directed downwards. Below this, another shallow groove, the palpebro-malar sulcus, 

 runs round from near the inner canthus of the eye, following fairly closely the lower 

 margin of the orbit. A small external palpebral sulcus is continued outwards from 

 the outer canthus for about 3 mm., and forms a prolongation of the palpebral cleft 

 when the eye is closed. Contraction of the outer part of the orbicularis palpebrarum 

 gives rise to radiating furrows outside and below the eye, markings which are 

 generally permanent in old persons. 



The skin of the eyelid is very soft and thin ; at the free margin of each lid it 

 passes into the conjunctiva along the line of the eyelashes, and within this a sharp 

 edge is formed, especially in the case of the lower lid, which is closely applied to the 

 surface of the eyeball. The palpebral fissure is somewhat oval, or widely fusiform, 

 in shape, but the margin of the upper lid is more arched than that of the lower. 

 The fissure is also generally a little inclined from without inwards and downwards. 



The whole length of the palpebral fissure is about 30 mm. (an inch and a 

 quarter) ; its breadth is scarcely sufficient, unless when the eyes are unusually widely 

 opened, to expose the whole of the cornea ; but these dimensions, especially the 

 latter, vary considerably in different persons, thus causing the eye to appear larger 

 or smaller, although the size of the globe itself is relatively very constant. At the 

 outer canthus, the lids meet in an acute angle ; at the inner, the fissure is prolonged 

 downwards and inwards for about 5 mm. between portions of the lid-margins, which 

 are straight and rounded. The junction of the curved and straight portions of the 



