Skull and Hyoid 221 



side of the groove known as the lingula. This appears to be only present as a guard for 

 the artery, but its morphological value is doubtful ; it has a separate centre of ossifica- 

 tion, and is laid down as a separate cartilaginous structure in the embryonic skull. 



The greaLwing or alisphenoid supports the anterior pole of the temporo-sphenoidal 

 lobe of tlWcerebrum, is therefore concave on its upper surface in all directions, forming 

 the front part of the middle fossa on each side, and exhibits impressions for the cerebral 

 gyri. The wing is tlu'ckened in front and externally, so that, in addition to its upper 

 and lower surfaces, it presents an anterior or orbital and an outer or temporal aspect. 



The upper concave cerebral aspect is in a very general way triangular, attached to 

 the body by the internal angle : the front border, raised, is separated from the small 

 wing by the sphenoidal fissure and, outside this, articulates with the frontal : the outer 

 and upper angle, raised, is blunt and articulates with the parietal : the outer or postero- 

 external border descends rapidly from this angle in a concave line that articulates 

 with the temporal squama and runs downwards, backwards, and inwards : the posterior 

 angle projects well back beyond the level of the rest of the bone and fits in between 

 the squamous and petrous temporal : the inner or postero-internal border, articulating 

 with the petrous, runs from this angle towards the body, where it is joined by the 

 lingula and marked by the carotid groove. This surface presents (Fig. 179) : 



(a) Foramen spinosum, in posterior angle, for meningeal vessels and recurrent 

 branch of mandibular nerve ; from this a groove for the anterior division of the artery 

 is usually found running along the postero-external border, but this is occasionally 

 on the temporal s'de of the suture. A small canalis innominatus is occasionally seen 

 internal to the foramen spinosum, for the passage of the small superficial petrosal 

 nerve. 



(b) Foramen ovale, for the mandibular division of the fifth nerve, its motor root, 

 and the small meningeal artery. 



(c) Foramen rotundum, for the superior maxillary division of the nerve. Notice 

 that this opening is just below the inner end of the sphenoidal fissure, and it may be 

 looked on as part of this fissure cut off by extending ossification. 



Articulate the bone with the temporal and observe the position of the Gasserian 

 ganglion (Fig. 181). It lies on the petrous and over the outer part of the foramen 

 lacerum, just behind and internal to the foramen ovale, into which its largest offset 

 goes. 



The other two divisions of the nerve, running to the foramen rotundum and 

 sphenoidal fissure respectively, are therefore internal to and above the mandibular 

 division and are in relation with the outer wall of the cavernous sinus. 



The bone is covered on this aspect by dura mater, and the nerves and artery lie 

 between it and the membrane, which extends from the front border of the wing on to 

 the lesser wing and thus covers in the sphenoidal fissure. 



The lower or basal aspect of the wing is small, and corresponds with the inner part 

 of the wing and with that portion that extends back to form the posterior angle : the 

 outer part of the wing is turned up, forming a continuous curve with the remainder 

 on the cerebral aspect, but being marked off from the lower surface externally by a 

 definite border or ridge, the inferior temporal crest. The basal surface can thus be said 

 to lie between this crest and the external pterygoid plate, while the temporal surface 

 lies above the crest. 



The basal surface gives origin to External Pterygoid from the whole of the surface 

 outside the pterygoid plate, the area of origin being bounded in front by the pterygoid 

 ridge, which turns outwards from the front of the plate and usually shows a pterygoid 

 spine to which some aponeurotic fibres on the superficial surface of the muscle are 



