OSSIFICATION OF FACIAL BONES. 



G9 



of six months ; 2*, additional nuclei for the lesser wings ; 5, separate lateral processes 

 of the body : the other indications are the same as in A. 



C, sketch of the back part of the bone shown in A ; 4, the internal pterygoid processes 

 still separate. 



D, the sphenoid at the usual period of birth. The great wings are still separate. 

 The anterior sphenoid is now joined to the body, and the internal pterygoid processes 

 (not seen in the figure) are united to the external. 



In the post-sphenoid part of the body two granules appear, placed side by side in 

 the sella turcica, and after their union two others appear, from which are formed 

 the parts on which are placed the carotid grooves. In the pre-sphenoid division the 

 first pair of nuclei appear outside the optic foramina, and extend by their growth into 

 the small wings : another pair of granules appear on the inner sides of the foramina, 

 and the pre-sphenoid portion of the body either results from the union of these, or 

 is an independent growth. The pre-sphenoid is united to the body of the post- 

 sphenoid long before the latter is united to the great wings. Their line of union is 

 indicated for some time by a hole filled with cartilage, round above, and opening 

 inferiorly into a wide notch, which is recognisable for several years after birth. The 

 body of the pre-sphenoid is for a year or two broad and rounded inferiorly, but 

 becomes gradually narrower and more prominent : it is separated at first by a layer of 

 fibro-cartilage from the sphenoidal spongy bones. The sphenoidal spongy bones 

 seldom appear till after birth : each is in early life a hollow pyramid formed by the 

 union of three separate laminae, viz., an inferior, an external, and a superior : the 

 inferior lamina forms the greater part of what can be distinguished in the adult ; 

 the external is that to which the orbital portion belongs ; while the superior lamina, 

 forming the inner wall and roof of the original sphenoidal sinus, becomes, as the 

 sinus expands, partly absorbed and partly united to the attenuated body of the pre- 

 sphenoid, which is ultimately reduced to the thin septum sphenoidale and the 

 rostrum. 



The ethmoid bone exhibits osseous deposit first in the orbital plates, whence it 

 spreads into the turbinated portions ; in its mesial part ossification begins above 

 and passes down into the nasal septum, and outwards into the cribriform plate. 



The superior maxillary bone commences to ossify at a very early period imme- 

 diately after the lower maxilla and the clavicle, and before the vertebrae. Its early 

 growth has not yet been sufficiently studied. Beclard (Meckel's Archiv., vi. p. 432) 



Fig. 63. DIFFERENT VIEWS OF THE SUPERIOR MAXILLARY BONE OF A FOSTUS OF FOUR 



OR FIVE MONTHS. 



A, external surface ; a fissure, 1, is seen extending through the orbit into the infra- 

 orbital foramen. 



B, the internal surface ; the incisor fissure, 2, extends from the foramen upwards 

 through the horizontal plate and some way into the nasal process. 



C, the bone from below, showing the imperfect alveoli and the incisor fissure, 2', 1, 

 which crosses the palatine plate, between the second and third alveolus, and passes 

 through the outer part of the bone. 



states that it consists at first of five pieces, viz., 1, an alveolar arch ; 2, a palatal part; 

 3, an orbital and malar ; 4, a nasal and facial ; 5, an incisor part. This, however, 

 does not appear to be a constant arrangement. In all young subjects, and sometimes 

 even in the adult, there is a fissure, the incisor fissure, passing outwards from the 

 incisor foramen to the alveolar border, in front of the canine socket. The part in 



