hbduCka] THE LOWER JAW 309 



become a racial character, albeit a variable one." And page 181 : 

 '• There seems to be no doubt whatever that it is a formation connected 

 with Arctic races or Arctic conditions of life; and, accordingly, it can 

 not safely be assumed to be a racial character, however difficult it is 

 to regard it as a formation only acquired individually." 



With both the previously published and the present data, I believe 

 the subject of these bony formations may now be approached with 

 some hope of definite conclusions. 



These hyperostoses give no indication of being pathological. They 

 are formed largely, if not entirely, by compact bone tissues of evi- 

 dently normal construction. They never show a trace of attending 

 inflammation or of ulceration or of breaking down. They resemble 

 occasionally the osteomae of the vault of the skull, and more dis- 

 tantly the osteomae of the auditory meatus, but in those cases 

 where the bony swelling is uniform and in many others they show to 

 be of quite a different category. (PI. 61.) 



As a rule these bony protuberances in the Eskimo are not con- 

 nected with evidence of pyorrhoea, root abscesses, or any other 

 pathological condition of the teeth, for those conditions are prac- 

 tically absent in the older Eskimo skulls ; therefore they can not be 

 ascribed to any irritation due to such conditions, and the Eskimo 

 have no habits that could possibly be imagined as favoring, through 

 mechanical irritation, the development of these bony swellings. 

 Wear of the teeth, which has been thought to stand possibly in a 

 causative relation to these developments, is common in many races 

 and even in animals (primates, etc.), without being accompanied 

 by any such formations. 



The development of such overgrowths is not wholly limited, as 

 already indicated from the cases reported by Danielli (1884) and 

 Virchow (1889), to the lower jaw, but somewhat similar growths 

 may also be observed, though much more rarely, both lingually and 

 on the outer border of the alveolar process of the upper jaw in the 

 molar region. When present in the latter position they interfere 

 with the measurement of the external breadth of the dental arch. 



But, if neither pathological themselves nor due to any pathological 

 or mechanical irritation, then these hyperostoses can only be, it would 

 seem, of a physiological, ontogenic nature ; and if so, then they must 

 be brought about through a definite need and for a definite purpose 

 or function. 



These views are supported by their marked symmetry, which is 

 very apparent even where they are irregular; by the fact that in 

 general they are not found in the weakest jaws (weak individuals) , 

 or again in the largest and stoutest mandibles (jaws that are strong 

 enough as it is) ; and by the history of their development. 



