Fig. 234.—Double Hare-lip in a girl æt. 17.
Fig. 235.—Double Hare-lip with Projection of Os Incisivum, in an infant before first dentition.
Cleft Palate.—It has already been mentioned that the palate is formed by the blending of the two palatal plates of the maxillary processes with the four segments of the os incisivum, derived from the nasal processes. The foramen incisivum (anterior palatine foramen) marks the point at which these elements of the palate unite. The process of fusion begins in front and spreads backwards, the two halves of the uvula being the last part to unite.
As development may be arrested at any point, several varieties of cleft palate are met with. The uvula, for example, may be bifid, or the cleft may extend throughout the soft palate. In more severe cases, it extends into the hard palate as far forward as the foramen incisivum. In these varieties the whole cleft is mesial. In still more aggravated cases, the cleft passes farther forward, deviating to one or to both sides in the fissures between the mesial and lateral segments of the os incisivum or between the lateral segments and the maxillæ. These cases are combined with double hare-lip.
The cleft varies considerably in width. It may be so wide that the imperfectly developed nasal septum is seen between its edges, and gives to the cleft the appearance of being double, or the septum is adherent to one edge of the palate—usually the right—and the cleft appears to be to the left of the middle line. In most cases the roof of the mouth is unduly arched, and is narrower than normal ([Fig. 236]).
