726 



CRANIUM. 



laterally, rough surfaces and processes for the 

 attachment of muscles concerned in deglutition, 

 also some of the foramina already referred to, 

 for the transmission of the vessels and nerves 

 of the throat to and from the interior of the 

 skull, as well as the surfaces on which the 

 lower jaw moves. 



The upper surface of the base conforming to 

 the base of the brain, there are larger depres- 

 sions on it for the anterior and middle lobes; a 

 deep pit or cavity for the cerebellum, and in 

 the centre a broad sulcus, which glides into that 

 pit, for the medulla oblongata, as well as strong 

 ridges and processes to afford attachment to the 

 membranous partitions which severally exist 

 between the cerebrum and cerebellum, the he- 

 mispheres of the former and the lobes of the 

 latter organ. 



Thebonesinto which the cranium is separable 

 or of which it is immediately formed, are eight, 

 viz. the sphenoid, the frontal, the ethmoid, the 

 occipital, the two temporal, and the two parietal. 

 The first named bone is so placed as to be in 

 connexion with all the others, and to have 

 them grouped around it ; so that the frontal 

 (F, fig. 370) and ethmoid are in its front, the 



Fig. 370. 



WM w^i^ r *' >; >' 



occipital (O, Jig. 372) is behind it, the two 

 temporal (T, jig. 370) are on its sides, and 

 the two parietal (P, fig. 370) are above it. 



The sphenoid bone (from atpnv, cuneus, os 

 sphenoidale ; Germ. Sphenoidal-knochen, Keil- 

 knochen) comprehends the quadrilateral mass 

 which forms the centre of the frame-work, the 

 anterior ribs which support the frontal and partly 

 the lateral domes, and the depending pillars 

 which form the boundaries of the face ; it extends 

 to each temple, is behind and in part forms the 

 orbits and the nose, and is also behind but in 

 close connexion with the bones of the face. 



The central portion is called the body, and 

 the diverging processes are named alae majores 

 and alee minores. 



The body is of a quadrilateral figure, hollow 

 and divided by a partition into two chambers 

 (the sphenoidal cells, s, jig. 371), which open 



through the medium of the posterior ethmoidal 

 cells into the superior iwatus of the nose. On 

 its upper surface is a deep depression fephip- 

 pii(in,!>ellu turcica, fossa pituitaris) for the lodge- 

 ment of the pituitary gland. The posterior bor- 

 der of this depression presents a crest, the corners 

 of wiiich are slightly tumid, (posterior ephip- 

 pial, or clinoid processes,) for the attachment of 

 the tentorium, and this crest is prolonged down- 

 wards and backwards under the name of the 

 basi/ar process, to join the process of the same 

 name of the occipital bone; on each side 

 there is a depression (sulcus caroticus) for 

 the reception of the internal carotid artery, 

 and which also marks the situation of the 

 cavernous sinus. OK its under surface may 

 be seen, on the median line, the processes 

 azi/gos (rostrum), which is wedged into the 

 base of the vomer, and on each side of it a line 

 indicating the articulation of the two plates of 

 which the vomer is formed. Still more out- 

 wardly there is a groove which is converted into 

 a canal by the application against it of the in- 

 ferior orbitary or sphenoidal process of the pala- 

 tine bone. 



Fig. 371. 



The anterior surface exhibits the openings of 

 the sphenoidal cells, having, between them, and 

 apparently a continuation of their septum, a 

 prominent ridge which articulates with the ver- 

 tical plate of the ethmoid, and, below them, the 

 triangular curved processes denominated the 

 turbinutcd 'processes of the sphenoid bone. Ex- 

 ternally to these foramina and turbinated pro- 

 cesses on each side is a rough line for the arti- 

 culation, in its two superior thirds, of the 

 orbital plate of the ethmoid, and, in its inferior 

 third, of theorbitar process of the palatine bone. 

 To the outer side of this rough line is a smooth 

 surface which contributes to the formation of 

 the orbit. 



The posterior surface is rough, quadrilateral, 

 and at an early age becomes indissolubly united 

 to the basilar process of the occipital bone 

 (d, Jig. 371); for which reason Scemmerring 

 and Meckel have regarded as one, the occi- 

 pital and sphenoid bones, and as such have 

 described it under the name of os basilare. 



This surface is bounded superiorly by the 

 basilar process before mentioned, which is 



