90 



OSTEOLOGY. 



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forwards, outwards, and downwards, is of an oblong form, and rough for articulation 

 with the superior maxillary bone. The posterior or sphenoidal surface is directed 

 backwards, upwards, and inwards. It ordinarily presents a small half-cellular 



cavity which communicates with 



Fig. 52. Left Palate Bone. Posterior View (enlarged). the sphenoidal sinus, and the 



margins of which are serrated 

 for* articulation with the vertical 

 part of the sphenoidal turbinated 

 bone. The internal or ethmoidal 

 surface is directed inwards, up- 

 wards and forwards, and articu- 

 lates with the lateral mass of the 

 ethmoid bone. In some cases, 

 the cellular cavity above-men- 

 tioned opens on this surface of 

 the bone; it then communicates 

 with the posterior ethmoidal 

 cells. More rarely it opens on 

 both surfaces, and then commu- 

 nicates with the posterior eth- 

 moidal cells, and the sphenoidal 

 sinus. The non-articular or free 

 surfaces are the superior or or- 

 bital, directed upwards and out- 

 wards, of triangular form, concave, 



smooth, articulating with tne superior maxillary bone, and forming the back 

 part of the floor of the orbit. The external or zygomatic surface, directed out- 

 wards, backwards and downwards, is of an oblong form, smooth, and forms part 

 of the zygomatic fossa. This surface is separated from the orbit by a smooth 

 rounded border, which enters into the formation of the spheno-maxillary fissure. 

 The Sphenoidal Process of the palate bone is a thin compressed plate, much 

 smaller than the orbital, and directed upwards and inwards. It presents three 

 surfaces and two borders. The superior surface, the smallest of the three, arti- 

 culates with the horizontal part of the sphenoidal turbinated bone ; it presents a 

 groove which contributes to the formation of the pterygo-palatine canal. The 

 internal surface is concave, and forms part of the outer wall of the nasal fossa. 

 The external surface is divided into an articular, and a non-articular portion ; the 

 former is rough for articulation with the inner surface of the pterygoid process 

 of the sphenoid; the latter is smooth, and forms part of the zygomatic fossa. 

 The anterior border forms the posterior boundary of the spheno-palatine foramen. 

 The posterior border, serrated at the expense of the outer table, articulates with 

 the inner surface of the pterygoid process. 



The orbital and sphenoidal processes are separated from one another by a deep 

 notch, which is converted into a foramen, the spheno-palatine, by articulation with 

 the sphenoidal turbinated bone. Sometimes the two processes are united above, 

 and form between them a complete foramen, or the notch is crossed by one or 

 more spicula of bone, so as to form two or more foramina. In the articulated 

 skull, this foramen opens into the back part of the outer wall of the superior 

 meatus, and transmits the spheno-palatine vessels and nerves. 



Development. From a single centre, which makes its appearance at the angle of 

 junction of the two plates of the bone. From this point ossification spreads, in- 

 wards, to the horizontal plate ; downwards, into the tuberosity ; and upwards, into 

 the vertical plate. In the foetus, the horizontal plate is much longer than the 

 vertical ; and even after it is fully ossified, the whole bone is remarkable for its 

 shortness. 



Articulations. With seven bones: the sphenoid, ethmoid, superior maxillary, 

 inferior turbinated, vorner, opposite palate, and sphenoidal turbinated. 



