MORPHOLOGY OF THE SKULL 



93 



tubercle or jugular process ; the squaiuo-occiijital presents two deep fissures separating the 

 interparietal fruni the suiiraoccipital portion, and extending nearly as lar inwards as the occipital 

 protuberance. The grooves for the lateral sinus are absent. 



The sphenoid in a macerated foetal skull falls into three pieces. The main ])ortion consists 

 of the united pre- and post-sphenoid with the orbito-sphenoids and lingulae. The pre- 

 sphenoid is quite solid and connected with the ethmo-vomerine cartilage, ami presents no traces 

 of the air siimses Mdiich occupy this ]iart in the adult skull. The pre-si)henoid by its upjier 

 surface forms part of the anterior cranial fossa, from which it is subsequently excluded by the 

 orbito-sphenoids. The optic ioramina are large and triangular in shape. The lingulae stand 

 out from the basi-sphenoid as two lateral buttresses, and the floor of the sella turcica presents 

 the cranio-pharyngeal canal, which in a recent bone is occupied by fibrous tissue. The dorsum 



Fig. 101. — TiiE Sphenoid at Birth. 



^^/?,'71'MT} 



VIDIAN CANAL LINGULA 



ephippii is yet cartilaginous. The ali-sphenoids with the pterygoid processes are separated from 

 the rest of the bone by cartilage. The foramen rotundum is complete, but the luture foramen 

 ovale is merely a deep notch in its posterior border, and there is no foramen spinosum. The 

 pterygoid processes are short, and each internal pterygoid plate presents a broad surface for 

 articulation with the lingulse. The Vidian canal is a groove between the internal pteiygoid 

 plate, the lingula, and greater wing. 



The temporal bone at birth consists of three parts (excluding the ear-bones) : the petrosal, 

 squamosal, and tympanic. The petrosal presents a large and conspicuous floccular fossa ; tlie 

 hiatus Fallopii is a shallow bay lodging the geniculate ganglion of the facial nerve. There is a 



\ 



Fig. 102.— The Temporal Bone at Birth. 



squamosal 



relatively large mastoid antrum, but no mastoid jnocess. The styloid process is uno.^sitied, but 

 the tympano-hyal may be detected as a minute rounded nodule of bone near the stylo-mastoid 

 foramen. 



The squamosal has a very shallow glenoid fossa and a relatively large post-glenoid tubercle. 

 The posterior part of the inferior border is prolonged downwards into an uncinate proce^s to 

 clo.se externally the mastoid antmm. 



The tympanic bone or annulus is a delicate horseshoe-shaped ossicle, attached by its aiiti rior 

 and posterior horns to the inferior l)order of the squamosal. 



The ear-bones are chiefly of interest from their size, for they are as large at birth as in the 

 adult. Tlie processus gracilis (Folian process) may be 2 cm. in length. 



