THE GLENOID FOSSA IN THE SKULL OF THE ESKIMO. 9 



great width of these palates, as compared with their length. 

 (The palato-maxillary length in these cases has been measured 

 from the mid-point of a line drawn across the hinder borders of 

 the maxillary bones, to a point between the anterior margins of the 

 central incisors ; hence this measurement is not strictly comparable 

 with those given by Dr. Keith as the measurements for the 

 Heidelberg, Gibraltar, and Jersey specimens). The form of 

 the palate in the Eskimo skull No. 1 illustrated here (see Plate IV), 

 is very typical of this horseshoe shape, and is very similar 

 to the palatal shape of the Gibraltar skull. As we have already 

 seen, the biting and chewing muscles are all in a high state of 

 development in the Eskimo skulls, while the external pterygoid 

 plates are noticeably large. Now the external pterygoid muscles 

 are the direct agents in the side-to-side grinding movement. 

 If the muscles on one side act, the corresponding side of the jaw 

 is drawn forward, and the other condyle remaining comparatively 

 fixed, the symphysis deviates to the opposite side. The alter- 

 nation of these movements on the two sides produces trituration. 

 When we turn to the teeth, although the roots do not show that 

 degree of specialization to which those of Mousterian man had 

 arrived, yet the form which the wearing down of their crowns 

 takes is very noteworthy. All the teeth are in the adult very 

 much worn down by attrition, the incisors and canines just as 

 much as, and sometimes even more than, the others. This 

 appearance is due to the fact that in this race, as indeed is the 

 general rule among all races living under primitive conditions 

 of food and cookery, the lower incisors are in apposition to those 

 in the upper jaw and do not, as in civilized races, bite behind 

 them. 1 Hence, in a side-to-side grinding movement of the 

 mandible, accompanied, as it will necessarily be, by antero- 

 posterior movements as well, the surface of the incisors would 

 play over each other to the same extent as those of the molars; 

 in addition to which must be taken into consideration also the 

 wear occasioned by the meeting of these teeth in biting move- 

 ments of the jaws. 



1 See "Craniology of Australians with reference to dentary arcade," 

 by Sir William Turner, Journ. Anat. and Phys., 1891. 



