54c Canadian Arctic Expedition, 1913-18 



Mandibles 



One of the first features that impressed the writer was the general massive- 

 ness of these Eskimo mandibles. 



All the muscle markings were most pronounced, thus providing a suggestive 

 reminder of the masticatory vigour of these individuals. Only in a few instances 

 had the teeth been missing at death, for the alveoli as a rule were deep and their 

 walls healthy. The angles were markedly everted. Indeed this eversion had 

 in many cases involved also the lower halves of the rami, thus imparting a very 

 broadened appearance to the jowls (Fig. 2). The writer was much surprised 

 at the obtuseness of the angles, considering that none of the individuals repre- 

 sented ages much above middle life. For example the sizes varied from 128° to 

 122° in the adult males and from 130° to 121° in the adult females. Thxis none 

 of them approximated to 90°. The inter gonial width was remarkably high, 

 ranging from 128 mm. to 115-5 mm. in the adult males and from 114-5 mm. to 

 101-3 mm. in the adult females. These high figures were of course a natural 

 result of the eversion of the angles. The highest intergonial measurement the 

 writer could make in a collection of male European mandibles proved to be 

 111-3 mm. and this was well below the minimum for the male Eskimo series, 

 as noted above. 



One of tlie striking features of these Eskimo mandibles was the marked 

 lowering of the posterior ends of the alveolar borders. This was most pronounced 

 when viewed from the side (Fig. 3). For example, in one adult male mandible 

 the height at the symphysis was 47 mm. and this rapidly diminished in a posterior 

 direction, until opposite the third molar tooth it was only 32-5 mm., represent- 

 ing a reduction of 31 per cent. This remarkable condition suggested to the 

 author a new index for the mandible to which he has applied the term "the index 

 of height of the mandible in the molar region." The height in front is measured 

 from the ridge between the alveoli of the central incisor teeth to the lower 

 border of the symphysis. The height posteriorly is taken from the inner edge 

 of the alveolus of the third molar tooth to the lower border of the mandible. 

 This measurement was always made on both right and left sides in these Eskimo 

 mandibles, for it was ascertained that in only three cases did these heights 

 agree on both sides. In the others there was always a slight difference, and in 

 these, interestingly enough, the lowering was on the right side, except in two 

 cases where it was on the left. This suggested of course that these Eskimos 

 were accustomed to masticate more on the right side than on the left. 



This new index was obtained by multiplying the height at the third molar 

 tooth by one hundred and dividing by the height at the symphysis. The result 

 of course represented the percentage height of the molar region. This proved 

 a profitable investigation, for it produced not only interesting but also consistent 

 results. For example it was found that the index progressively diminished with 

 age. This fact furnished an interesting side light on the masticatory habits 

 of the Eskimo, for it demonstrated that the terrific pressure to which the teeth 

 were subjected forced the lower molar series more and more downwards during 

 the period between adolesence and middle life. 



On making a close analysis of this new index it was noted that the highest 

 figiu-e, namely 91-4, was recorded in the mandible of a young adolescent female. 

 The minimum (62-1) was found in the mandible of an adult female. 

 The writer compared these results with the corresponding indices for ten Euro- 

 pean mandibles, where the maximum was 94 ■ 1 and the minimum 76 - 1 , showing 

 of course that the masticatory activity, and therefore the downward pressure 

 upon the lower molar series, were not nearly so evident in these types of mankind. 



This forcing downwards of the molar sockets produced an excessive broad- 

 ening of the posterior portions of these Eskimo mandibles. Thus the distance 

 between the inner border of the alveolus of the third molar tooth to the point 



