Eskimo Osteology c55 



on the external surface where the anterior border of the ramus joins the body 

 was as much as 21-5 mm. in one adult male mandible, while the minimum 

 (14-5 mm.) was found in an adolescent female. The corresponding maximum 

 in a series of European mandi,bl'es was 18 mm. The general effect produced was 

 to cause the sockets of the molar series to overhang the inner aspects of the 

 mandibles to a pronounced degree. This feature of the Eskimo mandible has 

 been already emphasized by Hrdlicka.(^^) Indeed in some instances the bony 

 thickening was excessive. For example, in mandible XIV H-8 the inward bulg- 

 ing of the bone was so marked that the transverse distance between the inner 

 surfaces of the body opposite the first molars was reduced to 21-5 mm. This 

 jaw had therefore an extraordinary appearance when viewed from below (see 

 Fig. 5) . The writer would regard these bulgings as bone buttresses built up by 

 nature to resist the excessive strain thrown upon the alveoli of the molar teeth. 

 He exhibited the mandibles to Prof. H. E. Friesell, Dean of the Dental Faculty, 

 University of Pittsburg, and this authority concurred in the opinion expressed 

 above. 



The writer has made a routine practice in his anatomy course of referring 

 to a faint groove for the lingual nerve on the inner aspect of the mandible 

 immediately below the last molar tooth, and has always expressed surprise that 

 this is not described in standard textbooks of anatomy. These Eskimo mandi- 

 bles all exhibited this important groove, which, indeed, was present in some 

 cases to a pronounced degree. He would, therefore, put forward a plea for a 

 fuller recognition of the clinical importance of this groove, seeing that there 

 exists by no means a remote possibility of the lingual nerve being lacerated in a 

 clumsy extraction of the third molar tooth. 



The rami, in conformity with the bodies of the mandibles, were very massive- 

 ly developed and exhibited strong muscle markings. The author decided to 

 experiment with a new index for the ramus to be termed "the index of width of 

 the ramus." To obtain this the width was multiplied by 100 and divided by the 

 height. The length was measured from the bottom of the sigmoid notch to the 

 lower border of the ramus in a direction parallel to the anterior and posterior 

 borders. The width was measured from the centre of the slight concavity in 

 the anterior border below the coronoid process and at right angles to the borders. 

 The lines representing the length and width of each ramus thus intersected at 

 right angles. It was found that the measurements varied for the right and left 

 rami of each mandible except in one case. Thus in half the cases the right 

 ramus was the wider, while in the others the left exhibited the greater relative 

 width, suggesting varying masticatory habits of these individtials. The index of 

 course indicated the proportion which the width of the ramus bore to its length. 

 It was found to vary from 93 • 02 to 68 ■ 6, and, moreover, exhibited one consistent 

 feature, namely — it increased with age in both sexes, up to middle life at any 

 rate. There were no aged mandibles to illustrate the condition of the index in 

 late life. The interpretation of these results obviously was, that the width of 

 the Eskimo ramus increased with age in both sexes up to middle life. On study- 

 ing this index in ten adult Anglo-Saxon mandibles, the maximum and minimum 

 figures were 67-8 and 52-3, which were much below the Eskimo averages, thus 

 demonstrating that the Eskimo ramus was relatively much wider than the 

 Anglo-Saxon. On studying this matter further in European types of mandible, 

 it was ascertained that the index of width of the ramus increased with age so 

 long as the teeth remained intact, and then diminished again if the individual 

 became edentulous. Altogether this comparative study of these Eskimo mandi- 

 bles provided some gratifying and suggestive results. 



The mandibular condyles were so placed that their long axes converged 

 upon the centre of the anterior edge of the foramen magnum as in the European 

 type. Their articular surfaces were, however, shghtly flatter in conformation 

 with the more shallow character of the Eskimo glenoid fossae. 



