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. 
