100 



THE SKELETON 



The greater comua projects upward and backward from the sides of the body. 

 The}' are flattened from above downward, thicker near their origin, and terminate 

 posteriori}' in a rounded tubercle to which the thyreo-hyoid ligament is attached. 



The lesser cornua are small conical processes projecting upward and back- 

 ward ojDposite the lines of junction between the body and the greater cornua, 

 and ^ by their apices give attachment to the stylo-hyoid ligaments; they are 

 connected to the body by fibrous tissue. Professor Parsons has shown that a 

 joint with a synovial cavity is common between the smaller and geater cornua. 

 The lesser cornua are sometimes partly or even completely cartilaginous in the 

 adult. 



Fig. 126. — Hyoid Bone Enlarged to show Muscular Attachments. (After 



F. G. Parsons.) 



Greater cornu 



Attachment to 

 digastric tendon 



Body of hyoid 



Middle con- 

 strictor 



Hyo-glossus 



The muscles attached to each half of the hyoid bone may be enumerated as follows: — 



Body Genio-hyoid, genio-glossus, mylo-hyoid, sterno-hyoid, omo- hyoid, stylo- 

 hyoid, thyreo-hyoid and hyo-glossus. 



Greater cornu Thyreo-hyoid, middle constrictor, hyo-glossus, and digastric. 



Lesser cornu Chondro-glossus, and middle constrictor. 



Ossification. — In the early months of intra-uterine life the hyoid bone is composed of 

 hyaline cartilage and is directly continuous with the styloid processes of the temporal bones. 

 Ossification takes place from six centres, of which two appear in the central piece of cartilage, 

 one on either side of the middle line, either just before or just after birth; soon after their 

 appearance, however, they coalesce to form the body of the bone (basi-hyal). The centre for 

 each of the greater cornua (thyreo-hyals) appears just about the time of birth, and for each 

 of the lesser cornua (cerato-hyals) some years after birth, even as late as puberty. (F. G. 

 Parsons.) The greater cornua and the body unite in middle life; the lesser cornua rarely anky- 

 lose with the body and only in advanced age. Professor Parsons has shown, however, that the 

 lesser cornua more frequently unite with the greater cornua. 



THE SKULL AS A WHOLE 



The skull, formed by the union of the cranial and facial bones already de- 

 scribed, may now be considered as a whole. Taking a general view, it is spheroidal 

 in shape, smooth above, compressed from side to side, flattened and uneven 

 below, and divisible into six regions: a superior region or vertex, a posterior or 

 occipital region, an anterior or frontal region, an inferior region or base, and two 

 lateral regions. 



(1) The Superior Kegion 



Viewed from above {norma verticalis) the skull presents an oval outline with 

 the broader end behind, and includes the frontal, parietals, and the interparietal 

 portion of the occipital. In a skull of average width the zygomatic arches are 

 visible, but in very broad skulls they are obscured. 



