178 OSTEOLOGY 





The Greater Cornua or Thyrohyals (cornua majora). The greater cornua 

 project backward from the lateral borders of the body; they are flattened from 

 above downward and diminish in size from before backward; each ends in a tubercle 

 to which is fixed the lateral hyothyroid ligament. The upper surface is rough 

 close to its lateral border, for muscular attachments: the largest of these are the 

 origins of the Hyoglossus and Constrictor pharyngis medius which extend along 

 the whole length of the cornu; the Digastricus and Stylohyoideus have small 

 insertions in front of these near the junction of the body with the cornu. To the 

 medial border the hyothyroid membrane is attached, while the anterior half of the 

 lateral border gives insertion to the Thyreohyoideus. 



The Lesser Cornua or Ceratohyals (cornua minora). The lesser cornu are two 

 small, conical eminences, attached by their bases to the angles of junction between 

 the body and greater cornua. They are connected to the body of the bone by fibrous 

 tissue, and occasionally to the greater cornua by distinct diarthrodial joints, 

 which usually persist throughout life, but occasionally become ankylosed. 



The lesser cornua are situated in the line of the transverse ridge on the body 

 and appear to be morphological continuations of it (Parsons 1 ) . The apex of each 

 cornu gives attachment to the stylohyoid ligament; 2 the Chondroglossus rises 

 from the medial side of the base. 



Ossification. The hyoid is ossified from six centers: two for the body, and one for each cornu. 

 Ossification commences in the greater cornua toward the end of fetal life, in the body shortly 

 afterward, and in the lesser cornua during the first or second year after birth. 



THE EXTERIOR OF THE SKULL. 



The skull as a whole may be viewed from different points, and the views so 

 obtained are termed the normae of the skull; thus, it may be examined from above 

 (norma verticalis), from below (norma basalis), from the side (norma lateralis), 

 from behind (norma occipitalis), or from the front (norma frontalis). 



Norma Verticalis. When viewed from above the outline presented varies 

 greatly in different skulls; in some it is more or less oval, in others more nearly 

 circular. The surface is traversed by three sutures, viz.: (1) the coronal sutures, 

 nearly transverse in direction, between the frontal and parietals; (2) the sagittal 

 sutures, medially placed, between the parietal bones, and deeply serrated in its 

 anterior two-thirds; and (3) the upper part of the lambdoidal suture, between the 

 parietals and the occipital. The point of junction of the sagittal and coronal suture 

 is named the bregma, that of the sagittal and lambdoid sutures, the lambda ; they 

 indicate respectively the positions of the anterior and posterior fontanelles in the 

 fetal skull. On either side of the sagittal suture are the parietal eminence and parietal 

 foramen the latter, however, is frequently absent on one or both sides. The 

 skull is often somewhat flattened in the neighborhood of the parietal foramina, 

 and the term obelion is applied to that point of the sagittal suture which is on 

 a level with the foramina. In front is the glabella, and on its lateral aspects are 

 the superciliary arches, and above these the frontal eminences. Immediately above 

 the glabella may be seen the remains of the frontal suture; in a small percentage 

 of skulls this suture persists and extends along the middle line to the bregma. 

 Passing backward and upward from the zygomatic processes of the frontal bone 

 are the temporal lines, which mark the upper limits of the temporal fossae. The 

 zygomatic arches may or may not be seen projecting beyond the anterior portions 

 of these lines. 



1 See article on "The Topography and Morphology of the Human Hyoid Bone," by F. G. Parsons, Journal of 

 Anatomy and Physiology, vol. xliii. 



* These ligaments in many animals are distinct bones, and in man may undergo partial ossification. 



