436 



MAMMALIAN ANATOMY 



FIG. 365. 



teeth; the premolars are very generally known as the bicuspids; and the 

 third molars, because of their late appearance, are the wisdom teeth. 



The human dentition differs in many ways from the typical car- 

 nivorous dentition of the cat. The teeth are planted in the jaws 



continuously without diastemata 

 (Fig. 365), close together, with 

 their crowns in contact, though 

 their basal portions near the gum 

 are separated by slight intervals. 

 The alveolar borders describe 

 regular parabolic curves ; the 

 curve of the upper jaw is 

 slightly larger than that of the 

 under jaw, hence the upper in- 

 cisors overlap the under incisors 

 and parts of the lower canines ; 

 but the grinding surfaces of the 

 other teeth strike together, the 

 under teeth not shearing within 

 the upper, as in the cat's jaw. 

 The upper and lower teeth alter- 

 nate in such manner that the 

 point of the upper canine comes 

 between the lower canine and 

 the first premolar, the first upper 

 premolar between the two lower 

 premolars ; the alternation then decreases until the last upper molar 

 alone strikes the last lower molar. 



The upper back teeth are vertical, but inclined slightly outward ; 

 the upper front teeth project forward to a varying degree, in some 

 specimens so slightly that they do not overlap the lower teeth. The 

 lower teeth are vertical, the molars inclining slightly inward. All the 

 teeth of one jaw are of about equal length ; none protrude much 

 farther from the gums than the others ; hence the masticating line 

 is nearly level. 



The number of the human teeth is variable because some of the 

 third molars, or wisdom teeth, frequently are absent, and sometimes the 

 upper lateral incisors fail to develop. 



THE SKULL, SEEN PARTLY IN FRONT AND ON 

 THE RIGHT SIDE. 



1, frontal bone; 2, parietal bone; 3, temporal bone, 

 squamous portion; 4, sphenoid bone, temporal sur- 

 face of its great wing; 5, ethmoid bone, orbital sur- 

 face ; 6, maxilla ; 7, malar bone ; 8, lachrymal bone ; 9, 

 nasal bone; 10, mandible; a, orbital plate of the frontal 

 bone; b, temporal surface; c, orbital surface of the 

 large wing of the sphenoid bone; d, mastoid portion 

 of the temporal bone; e, orbital surface of the malar 

 bone;/, orbital plate of the maxillary ; g, infraorbital 

 foramen; h, mental foramen; i, symphysis; j, ramus; 

 k, coronoid process; I, condyloid process; m, angle; 

 i), lachrymal fossa. 



