22 Proceedings of the Royal Physical Society. 



record the amount of this variation, but it ought to provide 

 very interesting figures. One might measure the distance 

 from the condyle of the mandible {a) to the alveolar border 

 between the incisor teeth and (b) to the lowest point of the 

 symphysis menti. Then, by presenting a percentage com- 

 parison between these two measurements, on the assumption 

 that the condylo-alveolar distance equals 100, we could indi- 

 cate the amount of chin projection as follows : — 



Condylo-mental diameter X 100 ^ , ^ ,. . ^. 



— ^ , , — -. , ^, 7 = Index of chin proiection. 



Condylo-alveolar diameter ^ 



I have applied this formula to the lower jaws of a number 

 of typical mammals with very striking results, but I have 

 not had the opportunity of determining whether there be a 

 racial character in this facial feature. 



Another important character which appears to be increasing 

 in frequency is the shortening of the alveolar borders of the 

 upper and lower jaws, in consequence of which we see jaws 

 unable to provide sufficient space for the accommodation of 

 the full complement of teeth. As a result, the size and 

 number of the teeth undergo gradual diminution. 



The nose is another feature in which a gradual process of 

 evolution may be seen. Among animals, the highest part of 

 the anterior bony orifice of the nose is always below the 

 level of the floor of the orbital cavity, whereas among human 

 beings the highest part of the anterior nares is always above 

 the level of the orbital floors. Apart from this arrangement 

 of the anterior nares, the measurement of the height and 

 width of the nose, calculated in reference to facial points, 

 reveals a gradual evolution from the wide, low nostril of the 

 animal and primitive Australian aboriginal, to the narrow, 

 high nostril of the modern European. 



The same is equally true of the orbital chambers, in which 

 a gradual transition may be traced from the low, wide orbit 

 of the Australian aboriginal, to the narrow and higher orbit 

 of the European. 



Similarly, evolution may be observed in the hard palate, 

 for whereas in animals, length rather than width is the chief 

 characteristic, width rather than length is its outstanding 



