58 THE BONES OF THE HEAD. 



THE INFERIOR TURBINATE BONE. 



The inferior turbinate or spongy bone is a slender lamina, attached by its 

 upper margin along the lateral wall of the nose, and projecting into the nasal cavity, 

 so as to divide the middle from the inferior meatus. It is slightly involuted, its 

 convexity looking inwards, and its lower margin is free, somewhat thickened, and 

 rolled upon itself. The attached margin articulates in its fore part with the inferior 

 turbinate crest of the superior maxillary bone, then ascends abruptly, forming the 

 lachrymal process, which completes the lachrymal canal and articulates with the 



Fig. 60. RIGHT INFERIOR TURBINATE BONE : A, INNER VIEW ; B, OUTER VIEW. (Drawn by D. Gunn.) 



lachrymal bone ; behind this it is folded downwards in the maxillary process, forming 

 part of the inner wall of the antrum below the entrance into that cavity (fig. 69) ; 

 above and behind this, it presents a variable projection, the ethmoidal process, which 

 articulates with the uncinate process of the ethmoid ; and posteriorly it is attached 

 to the inferior turbinate crest of the palate bone. The posterior extremity is 

 elongated, sharp and pointed ; the anterior flattened and broader. 



This bone is marked by irregular pits, grooves and canals for vessels, which are 

 directed for the most part longitudinally, but not, as the turbinal parts of the ethmoid 

 are, with vertical grooves for the olfactory nerves. 



THE INFERIOR MAXILLARY BONE. 



The lower jaw, inferior maxilla, mandible, is the thickest and strongest bone of 

 the face, and moves on the rest of the skull by means of a pair of condyles articu- 

 lating with the glenoid fossae of the temporal bones. It has the shape of an inverted 

 arch bent forwards upon itself, and consists of a middle larger nearly horizontal 

 part the body, and of two ascending branches or rami. 



The body is marked in the middle line in front by a faint vertical ridge, indicating 

 the symphysis or place of union of the originally separate lateral parts : this expands 

 below into the triangular elevation of the chin, or mental protuberance, the base of 

 which is in well-marked bones slightly depressed in the centre, and prominent on 

 each side, forming the mental tubercle. The superior or alveolar border of the body 

 is hollowed out into sockets for the teeth. The inferior border or base is thick and 

 rounded, and projects beyond the superior. On the outer surface, on each side of 

 the symphysis, below the incisor teeth, is a shallow depression, the incisor fossa ; and 

 more externally is the mental foramen, placed midway between the upper and lower 

 borders, and under the interval between the two bicuspid teeth ; it is the anterior 

 opening of the dental canal, and transmits the mental nerve and vessels. Close below 

 the foramen is the somewhat indefinite external oblique line, running from the 

 mental tubercle backwards and upwards to the anterior margin of the ramus. The 

 deep surface is marked, on each side of the symphysis, along the inferior margin, by 

 an oval depression, indicating the anterior attachment of the digastric muscle. 



