OSTEOLOGY. 31 



In advanced age the loss of the teeth and alveolar borders 

 greatly reduces the body, the mental foramen opens near the 

 alveolar border, and the rami are united at very obtuse angles 

 with the base. 



THE HYOID BONE, or lingual bone, is a small U-shaped bone 

 situated at the base of the tongue, consisting of a body, two 

 greater and two lesser cornua. 



It is supported by the stylo-hyoid ligament from the styloid 

 processes of the temporal bones. 



The anterior surface is divided by a crucial ridge into four 

 depressions for muscular attachments, and its centre presents a 

 tubercle. 



The posterior surface is in relation with the epiglottis, being 

 separated by the thyro-hyoid membrane. 



The upper and lower borders afford attachment to muscles, 

 and the lateral surfaces are mounted with cartilage for articula- 

 tion with the greater cornua. 



The greater cornua, or thyro-hyals, project backward, afford 

 attachment to the hyoglossus, thyro-hyoid, and middle constrictor 

 of the pharynx, and terminate behind in a tubercle for the at- 

 tachment of the thyro-hyoid ligament. 



The lesser cornua, or cerato-hyals, are two tuber-like pro- 

 jections attached at the junction of the body with the greater 

 cornua, and receiving the insertion of the stylo-hyoid ligaments. 

 They do not articulate with any bone. 



Its muscular attachments are ten the lingualis, hyoglossus, 

 genio-hyoglossus, middle constrictor, stylo-, mylo-, genio-, sterno-, 

 thyro-, omo- hyoid ; also aponeurosis of digastric and stylo-hyoid 

 ligament. 



Ossific centres, five one for body and one for each horn. 



THE SUTURES AND FONTANELLES. The sutures are divided 

 into three sets, those of the vertex, side, and base of the skull. 



At the vertex of the skull there are three : 



Sagittal, or inter-parietal; 

 Coronal, or fronto-parietal; 

 Lambdoid, or occipito-parietal. 



At the side of the skull are three : 



Spheno-parietal ; 

 Squamo-parietal, or squamous; 

 Masto-parietal. 



At the base of the skull are nine : 



Basilar, in centre, 

 iVtro-orripiml. - 



Squaxno-Bphenoidalj 



