The development of the intermaxilla from two centres on each side may be accepted as a proven fact. It was first maintained by the late Mr. Callender,[48] who stated that these bones have a lateral wedge-shaped sutural surface, fitting into a groove in either superior maxilla, and that the alveolar processes of the latter extend forwards, forming the anterior walls of the sockets of the central incisors, and so fix the bones in position. A confirmation of the idea that the anterior alveolar walls of the incisor teeth are formed in this way was sought in the well-established fact that these particular parts are very imperfectly developed in those cases of alveolar harelip in which the os incisivum is isolated from the superior maxillæ; but such is probably due to the abnormal condition and position in which the bone is developed, rather than to the loss of the maxillary “clip.” And certainly the most recent researches tend to prove that the maxillæ have no share in the formation of the alveoli of the incisor teeth. Sir William Turner and other anatomists have fully confirmed this method of development from four ossific centres, and important additions to our knowledge of the subject have been made recently. Thus M. Gilis[49] describes and figures the condition of the palate as seen in a six-months fœtus, where it was clearly demonstrated that the intermaxillary portion formed a sort of lozenge-shaped prism fitting in between the two maxillæ, and consisting of four portions of bone, the sutures between these being perfectly clear and distinct (Fig. 35). The posterior extremity of the short axis of the intermaxillary segment corresponds to the anterior palatine canal, and the anterior surface forms the median anterior alveolar border, no process of the superior maxilla closing in the alveoli in front. The upper border of the bone forms the floor of the nasal apertures. [Illustration: FIG. 35.—Bony palate of a fœtus of six months, showing the development of the intermaxilla in four portions. _a._ Endognathion. _b._ Mesognathion. _c._ Exognathion. _d._ Anterior palatine canal. _e._ Endo-mesognathic suture.[50] _f._ Exo-mesognathic suture. (After _Gilis_.)] Biondi, of Breslau,[51] has completed the observations necessary for the establishment of this fact by demonstrating the four actual points of ossification in many fœtal skulls of different dates, which had been specially prepared for the purpose. Moreover, as mentioned before (p. 27), traces of the five intermaxillary sutures, when looked for, may be found in many adult and in the majority of young skulls.