THE FACE. 



1379 



} (2) through the canine fossa, lateral to the prominence caused by the root of the 

 canine tooth ; or (3) through the lateral wall of the inferior meatus of the nose. 

 In an antero-posterior skiagram of the skull, the shadow of the maxillary sinus 



r presents a pyramidal outline, the base corresponding to the floor of the orbit and 



<the rounded apex to the alveolar recess of the sinus. Sometimes the floor of the 



sinus extends medially, below the floor of the nose, into the palatine process 

 of the maxilla so as to form a distinct palatine recess. The medial outline 

 of the sinus area is formed by the foreshortened shadow of the nasal wall of the 



.sinus and the lateral pterygoid lamina, while laterally it is outlined by the 



: zygomatic bone. The petrous portion of the temporal bone throws a deep shadow 

 across the superior half of the sinus. In taking the skiagram, therefore, the head 



j should be placed in such a position that this shadow is raised as much as possible 

 into the orbits. In the living subject the inferior and medial portion of the outline 

 of the maxillary sinus is considerably obscured by that caused by the cervical 

 portion of the vertebral column (Killian). 



In a profile skiagram of the facial region of the dried skull, the shadow of the 



outline of the maxillary sinus is well defined. It is represented below by the 

 dense horizontal shadow of the hard palate which crosses the tips of the roots of 

 the molar teeth. Above it is limited anteriorly by the dark curved shadow of 

 the floor of the orbit, while above and posteriorly is the shadow of the posterior 

 ethmoidal-cell area. Behind the maxillary area are the vertical linear shadows 

 of the pterygoid laminae overlapped by that of the coronoid process of the mandible. 

 The anterior part of the sinus area is overlapped and, to a considerable extent, 



lobscured by the shadow caused by the denser and somewhat triangular shadow of 



.the zygomatic bone. 



Lips. In compressing the labial arteries, it must be remembered that they run 



; under cover of the mucous surface, a short distance from the free margins of the lips. 

 The lips are abundantly supplied with mucous glands which can be felt immediately 

 beneath the mucous membrane nearer their attached than their free borders ; the 



: glands are a frequent source of mucous cysts; occasionally they are enlarged 

 aongenitally, giving rise to one form of hypertrophy of the lip. 



Hare-lip is due to failure of the union of the superficial parts of the median nasal sub- 

 division of the fronto-nasal process with the maxillary process (Fig. 1079). The deformity 



j is spoken of as complete or incomplete accord- 

 ing as the cleft extends into the nostril or 

 merely involves a portion of the lip. The 

 fissure may involve the lip only, or it may 

 nclude the alveolar process of the maxilla ; in 



'the latter case the cleft may or may not be 

 issociated with a cleft of the palate. Lastly, 



':he hare-lip may be single or double, accord- 



< ng as the deficiency has occurred on one 



/usually the left) or both sides. 



Fig. 1080, taken from a coronal section 

 through the head of a human embryo at the 

 seventh week, shows how the mouth is shut 

 )ff from the nasal cavities by the growth in- 



( *vards from the deep aspect of the maxillary 



process of two horizontal plates (palatine 

 processes) which unite in the median line with 



! 3ach other and with the inferior border of Fl - 1079. -HEAD OF HUMAN EMBRYO ABOUT 29 



septum of the nose; the latter, which 

 ievelops as a downgrowth from the primitive 

 3asis cranii, is continuous anteriorly with the 

 :wo medial nasal processes which form the 

 jremaxillee and the median portion of the 

 ipper lip. The various degrees of cleft palate 

 .ire due to the more or less complete failure of union of the palatine processes with 

 ;ach other and with the premaxillary part of the median nasal processes. The olef t in the 

 soft palate, which is always median, may be either partial or complete, and mayor may 



88 a 



Globular process 



Olfactory 

 pit 



processes, the intervention of the olfactory pits 

 between the median and lateral nasal processes, 

 and the approximation of the maxillary and 

 lateral nasal processes, which, however, are 

 separated by the oculo-nasal sulcus (from His). 



