ia8 SURGICAL APPLIED Ax ATOMY, tchap. vin. 



alveolus, the cleft will leave the middle line and will 

 follow the suture between the superior maxillary bone 

 and the os incisivum, appearing therefore between the 

 incisor and canine teeth. Sometimes at the end of the 

 cleft the upper lip is fissured (hare-lip). Hare-lip is ex- 

 ceedingly rare in the middle line. The slit usually corre- 

 sponds to the suture just named, and is therefore oppo- 

 site the interval between the lateral incisor and canine 

 teeth. Sometimes the cleft in the palate on reaching the 

 alveolus will run on either side of the os incisivum, so 

 that that bone is entirely separated from the superior 

 maxilla. Such cases are associated with double hare- 

 lip, and the os incisivum appears as a nodule attached 

 to the nose and suspended in the centre of the gap. 

 The bone in these cases contains, as a rule, the germs 

 only of the central incisors, the lateral incisors having 

 been lost in the cleft. Hai-e-lip very commonly exists 

 without any cleft of the palate. Except in very rare 

 instances, a cleft of the hard palate will not exist with- 

 out a cleft of the soft. In some cases the os incisivum 

 may be entirely absent, and then the double hare-lip 

 that exists may appear as a large median gap in the 

 lip. When the hard palate is entirely cleft the edges 

 of the cleft are more or less perpendicular, whereas 

 when the cleft is very slight as regards its antero-pos- 

 terior length, the palate tends to preserve more or 

 less of its normal curve. 



The buccal cavity, when first formed in the foetus, 

 exists as a wide cleft in the face bounded above by the 

 fronto-nasal process, at the sides by the superior maxil- 

 lary processes, and below by the first visceral arch, 

 around which the lower jaw is formed. The nasal 

 and buccal cavities are one. " The separation of the 

 cavity of the mouth, strictly so called, from the nasal 

 fossae, is effected by the development of the palatal or 

 pterygo-palatal processes of the maxillary plate, which, 

 advancing inwards from the two sides, meet and 



