OSTEOLOGY AND SYNDESMOLOGY. 1") 



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■magnum {pi 121, fig. 17'), through which pass the mediiHa oblongata, the 

 vertebral arteries and veins, and the spinal accessory nerves ; on each side 

 are seen the condyles {fi^. 6*, 17') or surfaces of articulation between the 

 head and the vertebral column, constituting a hinge-joint by which the for- 

 mer may be moved backwards and forwards. In a depression behind each 

 condyle is the posterior conchjloid foravien, which conducts a cervical vein 

 to the lateral sinus. There is likewise the anterior conchjloid foramen for 

 conducting the hypoglossal nerve to the tongue. On the interior surface, 

 behind the foramen magnum, is seen a rectangular cross {fig. 18''^), form- 

 ing at the centre the internal occipital protuberance. To this cross the 

 dura mater is attached, and it also exhibits the impressions of cerebral 

 bloodvessels. In the angles of the cross are seen broad concavities, the 

 two superior of which receive the posterior lobes of the cerebrum, and the 

 two inferior those of the cerebellum {fi^. 18'' '). 



Anterior to the lower part of the occipital bone, and placed transversely 

 in the middle of the base of the cranium, is the sphenoid bone, os sphe- 

 noideum {pi. 122, fig. 6 above, fig. 7 below). In the middle of this highly 

 complicated bone is seen the body or centrum, which is hollow and contains 

 the sphenoidal sinuses {pi. 123, fig. 2 ', fig. 3 " ), communicating with the nose. 

 A deep depression on the upper surface, bounded anteriorly and posteriorly 

 by projecting spines and ridges, is the sella turcica for the reception of 

 the pituitary gland {pi. 122, fig. 6'). The inferior surface presents a 

 longitudinal rising in the middle called the sphenoidal or azygos process 

 {fig. 7 ' ), for articulation with the vomer. From the upper anterior part 

 of the body arise, one on each side, the apophyses of Ingrassias, the ensiform 

 processes or the little toings {fig. 6*), with the bases perforated by the foramen 

 opticum for transmitting the optic nerve with the ophthalmic artery. The 

 two great wings, al<x. magnce {fig. 7 '■ " ), arise from the sides of the body by 

 a small irregular base. They present three faces : one anterior, called 

 orbital from its forming part of the orbit ; one external, called temporal ; 

 and a third turned towards the brain, forming part of the fossa, for contain- 

 ing its middle lobe. Between the great and the small wings is a consider- 

 able fissure called ybra7ne?i sphenoidale, or foramen lacerum super ius {fig. 6°), 

 for transmitting the third, fourth, sixth, and first branch of the fifth pairs 

 of nerves and the ophthalmic vein. Below the base of this hole is ihe fora- 

 men rotundum {fig. 6') for the passage of the second branch of the fifth pair, 

 and behind the foramen rotundum again, is the foramen ovale {fig. 6*) for 

 the exit of the third branch of the fifth pair. About two lines behind the 

 foramen ovale is the foramen spinale {fig. 6') for transmitting the middle 

 artery of the dura mater. 



From the lower part of the two great wings project downwards on each 

 side the two pterygoid processes constituting the posterior portion of the 

 mouth {fig. 6 ' ). They serve for the attachment of certain muscles, and 

 are pierced at their base by the pterygoid foramen for transmitting the 

 nerve of the same name. 



The sphenoid bone articulates above and in front with the vomer, the 

 frontal, ethmoidal, malar, and parietal bones, laterally with the temporal, 



ICONOGRAPHIC EXCTCLOP.tDIA. VOL. II. 46 721 



