70 BONES OF THE HEAD. 



front of this fissure namely, that which bears the incisor teeth forms in all 

 mammals except man a separate bone, the intermaxillary or premaxillary ; and 

 anatomists have therefore sought with great care for proofs of its original independence 

 in the human subject, but it does not appear that even in the earliest stages of develop- 

 ment it has been seen by any one entirely unattached to the rest of the bone, or that 

 its line of suture has been traced upon the facial surface. On the other hand, in 

 cases of completely cleft palate, the bones supporting the incisor teeth are placed on 

 a projecting portion of bone, which is articulated to the fore part of the vomer, and 

 is entirely detached from the superior maxillary bones. 



The palate bone is formed from a single centre, which is deposited at the angle 

 between its horizontal and ascending parts. 



Fig. 64. Fig. 64. THE F(ETAL VOMER NEAR THE TIME OF BIRTH. 



1 & 2 show the two plates of which the bone consists, and 

 which are united behind and below. 



The vomer begins to ossify posteriorly near the upper part. 

 It consists at first of two laminas united posteriorly and 



inferiorly. The inferior border afterwards exhibits a flat surface marked by a mesial 

 line, which articulates with the maxillary and palate bones and ends abruptly behind 

 the crista nasalis. The margins of this surface become gradually absorbed. The ap- 

 pearance of a mesial plate does not take place for a little time after birth. 



The malar, nasal, lachrymal, and inferior turbinated bones are each ossified from a 

 single centre. 



Fig. 65. Fig. 65. THE INFERIOR MAXILLA OF A 



CHILD AT BIRTH. 



a & 5 indicate the two portions separate 

 at the sympbysis. 



The inferior maxilla begins to ossify be- 

 fore any other bone except the clavicle. It 

 consists of two equal lateral parts, which 

 are still separate at the time of birth. The 

 ossific matter is at first deposited in fibrous 

 tissue, and later in cartilage. Some ob- 

 servers admit only a single ossific centre 

 for each side (Nesbitt and Meckel) ; while, 



according to others, in addition to the main piece there are separate nuclei for the 

 coronoid process, the condyle, the angle, and the inner side of the alveolus (Spix), 

 or only for some of these parts (Kerckringius, Be"clard, Cruveilhier). The dental canal 

 is at first a simple open groove. As in the superior maxilla the alveoli are gradually 

 developed from the groove by its division into compartments by partitions of subse- 

 quent growth. 



The hyoid bone has five points of ossification one for the body, and one for each 

 of its great and small cornua. The ossification begins in the great cornua, and soon 

 follows in the body in the last month of foetal life. 





PERIODS OF OSSIFICATION OF THE BONES OF THE SKULL. 



In the occipital bone 



Ossification of the tabular part appears in the 7th week (foetal life). 

 Ossification of the basilar part appears in the 7th or 8th week. 

 Ossification of the condyloid part appears in the 7th or 8th week. 

 The condyloid and tabular parts unite in the 4th year. 

 The basilar and condyloid parts unite in the 5th or 6th year. 



In the parietal bone ossification appears in the 7th or 8th week. 

 In the frontal bone ossification appears in the 7th week. 



The parts of the frontal bone unite in the course of the 2nd year. 



