58 



THE HUMAN BODY 



c 



foramen magnum is an occipital condyle (Fig. 29, oc). These 

 are the points at which the skull rests upon the atlas. The orbits 



or eye sockets are outlined in front 

 by the frontal, malars, and max- 

 illae. The space behind the orbit, 

 between the malar and temporal 

 bones, is occupied by a large mus- 

 cle which closes the jaw. The shape 

 of the face depends very largely 

 upon the malar bones. The an- 

 terior nares, or openings of the nos- 

 trils are bounded by the maxillse 

 and nasals. The posterior nares, by 

 which the nose communicates with 

 the throat cavity, lie behind the pal- 

 FIG. 29. The base of the skull, ate bones (Fig. 29) . Enlargements 



The lower jaw has been removed. ., ., t j.*. 



At the lower part of the figure is of the temporal bones contain the 



the hard palate forming the roof of Qlir |if r . v , r aT^T-iaya+na 

 the mouth and surrounded by the auditory apparatus. 



upper set of teeth. Above this are The Hyoid. Besides the cranial 



the paired openings of the posterior . " 



nares, and a short way above the and facial bones there is, as already 



the atlas, on its sides; 



vomer; pt, the palatines. 



v, 



pointed out, one other, the hyoid 

 (Fig- 30), which really belongs to 

 the the skull, although it lies in the 



, T . , ,. ,, . ,, 



neck. It can be felt in the front 

 of the throat, just above "Adam's apple." The hyoid bone 

 is U-shaped, with its convexity turned ventrally, and con- 

 sists of a body and two pairs of processes called cornua. The 

 smaller cornua (Fig. 30, 3) are attached to the 

 base of the skull by long ligaments. The bone 

 serves as an attachment for the base of the 

 tongue. The hyoid is of much interest from the 

 standpoint of comparative anatomy because in FIG. so. The hy- 



,. TT -r. i -^ r oid bone. 1, body; 



the very young Human Body it is part of a 2, great cornua; 3, 

 structure which corresponds to the gill mechanism snu 

 of fish, tadpoles, and similar aquatic animals, consisting of several 

 gill arches with gill clefts between them. In the human embryo 

 the gill clefts close before birth, and all the gill arches disappear 

 except those which persist as the hyoid. It is difficult to explain 

 the development and subsequent disappearance of this structure 



