HYOID BONE. 55 



down from the sharp inferior margin of this foramen is the mylo-lnjoid 

 qroove (occasionally a canal for a short space), marking the passage of 

 the mylo-hyoid nerve with an accompanying artery and vein. Behind 

 this, inside the angle, is a marked roughness for the internal pterygoid 

 muscle. 



Each ramus is surmounted by two processes, the condyle and tlie 

 coronoid, which are separated by a deep excavation, the .?if/moid notch. 

 The condyle is continued upwards from the posterior part of the ramus. 

 It is supported by a constricted portion, the nec}c,v;\\\di presents anteriorly 

 a depression, into which the external pterygoid muscle is inserted. The 

 condyle is a transversely elongated convex articular process, whose 

 major axis is directed obliquely, so that if prolonged it would meet 

 with that of its fellow near the anterior margin of the foramen magnum. 

 The coronoid process is continued vertically upwards in front, from the 

 anterior margin of the ramus. It is pointed, and gives attachment by 

 its margin and inner aspect to the temporal muscle. At its base, in 

 front, is a groove, to which the buccinator muscle is attached. 



The anterior marg-in of the ramus is placed at nearly a right angle to the 

 alveolar border. The angle of the jaw, which is the meeting of the posterior 

 border of the ramus with the base, is in the adult usually about 120^^ ; in infancy 

 it is as gTeat as 140^ or more ; in strongly developed jaws it may be diminished to 

 110° or less; and in old and toothless jaws it is increased. These changes are 

 connected with a variety of circumstances, among which may be noticed, — the 

 development of the temporaiy and permanent teeth, the absorption of the 

 alveolar arch after the loss of the teeth in advanced age. the elongation of the 

 face and upper jaw towards adult life, and the varying state of development of 

 the masseter muscles at different periods, 



THE HYOID BONE. 



The hyoid bone, or os linguce, is situated at the base of the tongue, 

 and may be felt between the chin and the thyroid cartilage. It is 

 shaped like the letter u, and consists of a body and two pairs of cornua. 

 It is suspended from the tips of the styloid processes of the temporal 

 bones by a pair of slender bands, the sfylo-hijoid ligaments, which in 

 most animals usually form distinct bones. Though belonging rather to 

 the neck than to the cranium or face, it may properly be considered in 

 this place. 



Fig. 48. — The IlroiD Bone, from befoke. | Fig. 48. 



1, the prominent part of the body ; 2, the great cornu ; 

 3, the lesser cornu. 



The hody, or central piece, hasi-hyal, is com- 

 pressed from before backwards, and lies in a 

 plane, directed downwards and forwards. Its 

 anterior surface is convex, and marked in the middle by a vertical 

 ridge, on each side of which are depressions for the attachment of muscles. 

 Its posterior surface is concave, and is directed towards the epiglottis. 



The great cornua, thyro-hyals, project backwards from the sides of the 

 body, and end in rounded extremities. 



The small cornua, or cornicula, cerato-hyals, short and conical, project 

 upwards and backwards from the place of junction of the body with 

 the great cornua, and give attachment at their extremities to the stylo- 



