Skull and Hyoid 271 



before twenty-five ; the styloid process is not joined to the temporal until middle life ; the vomer 

 and mcscthmoid are synostosed after forty-five ; and the skull in old age is edentulous, with \\.istcd 

 alveolar processes, and is lighter and has thinner bones with large air sinuses. 



It must be remembered that female skulls are thinner and lighter than male : they are shorter 

 in proportion to their breadth : they are also smaller, with a capacity about one-tenth less, but this 

 is in proportion to the smaller bulk of the female body.* The male skull is rougher and more 

 ridged, with more prominent mastoid processes, zygomatic arches, and occipital protuberance : 

 the superciliary ridges are more rounded and prominent, but the parietal eminences are less marked 

 than in the female skull. . In other words, the female skull preserves somewhat an appearance of 

 immaturity. The tympanic plate is said to be more developed in the male and shows a sharp 

 border, while in the other sex the edge is more rounded. The female palate is narrower than the 

 male. There is little sexual difference before puberty. 



In comparison of skulls of different races it is always advisable, when possible, to compare 

 the measurements of male skulls. For such measurements and indices the student must consult 

 works dealing with anthropometry, but a few may be given here as they are in common use : 



(a) Maximum length male, about 8 inches or less ; female, about inch less. 



(b) Maximum circumference (varies between 17^ inches and 21 J inches). In Europeans 

 male, about 2oJ inches ; female, about igj inches. 



max. breadth 



(c) Cephalic index : - x 100 = ceph. md. 



max. length 



Ceph. ind. of Europeans is 75 to 80 (mesaticephalic). 

 ,, ,, some races is over 80 (brachycephalic) . 

 ,, ,, others is under 75 (dolichocephalic). 



Usually rather larger in women than in men, owing to relatively greater breadth. 

 (All these measurements must of course be made between the same points if they are to have any 

 value in comparing different skulls, and these points are not always similar in the measurements 

 given by individual observers.) 



(d) The Facial Angle. This estimates the amount of prognathism or projection of the face 

 bones. It is obtained in various ways, depending in general en a basal skull line contrasted 

 with a line drawn from the nasion to a projecting point on the upper jaw. The contained 

 angle is the one required. In older measurements the opposite angle was taken, so that the 

 angle increased as prognathism decreased. 



It may not be out of place to point out here that the anthropoid skull is most like the human 

 type in its young state, diverging from it as it develops. The skull of a chimpanzee is distinguished 

 from that of man by the sloping plane of its foramen magnum already mentioned, the smallness 

 of its condyles, the diastema in the canine region of its jaws, its large intermaxillary bone, jaws, 

 teeth, and petrous bone, the want of a crista galli and flatness of its (usually fused) nasals, and the 

 presence of a well-marked post-glenoid process. In this last character the negro skull resembles 

 it to some extent. 



HYOID. 



A U-shaped bone situated in the ventral floor of the pharynx below the base 

 of the tongue and in front of the epiglottis. It presents a median unpaired body, 

 a long large cornu on each side, and a small nodule, not always bony, the small cornu, 

 situated above the junction of body and great cornu. 



The body is concave on its deep or posterior surface, lodging here the infra-hyoid 

 bursa : the bursa lies in front of the thyro-hyoid membrane, which is therefore attached 

 to the upper margin of the posterior surface. The anterior surface is convex and divided 

 by a transverse horizontal ridge into an upper and lower portion : the surface gives 

 attachment to muscles of the tongue and floor of the mouth and along its lower edge to 

 infra-hyoid muscles (Omo hyoid, Thyro-hyoid and Sterno-hyoid). 



The greater cornu, flattened, has usually an upper surface that gives origin to 

 Hyo-glossus and Middle Constrictor, a lower surface that has Thyro-hyoid and thyro- 



* The female skull is relatively larger : compared in weight with the rest of the skeleton it gives a 

 ratio i : 6. Male ratio i : 8. 



