354 



DR MATTHEW YOUNG. 



group of L58 the parietal arc was greater than the frontal in 55 cases and equal to 

 it in 7. In the " K" series the parietal arc was greater than the frontal in 25 cases 

 and equal to it in 8. As Turner writes : " It is the rule, therefore, for the parietal 

 ;ind frontal longitudinal arcs to exceed the occipital, though exceptions to the rule 

 occur in recognisable numbers." And further : ' k It is obvious, therefore, that so much 

 variation occurs in the relative length of the longitudinal arcs, they have no appreci- 

 able value as race characters in the Scottish skulls, and the variation occurred in both 

 the brachycephalic and dolichocephalic types." Evidence which may have an influence 

 in modifying the last statement will be supplied later when we come to consider the 

 correlation that exists between the total arc and its various segments, frontal, parietal, 

 and occipital, and between these segments and the glabello-occipital length in the 

 present series of Scottish skulls. As has been noted by several observers, including 

 Huschke, Welsbach, and Cleland (15), the relative proportions of the various 

 segments not only differ in the two sexes, but undergo a change during the course 

 of development, and evidence in support of this is supplied by the values in the 

 series of juvenile skulls. 



W ith regard to the other measurements in the two series of Scottish skulls, we 

 find that the mean basi-alveolar lengths are approximately equal, and the same relation- 

 ship holds with regard to the nasi-alveolar lengths. As a consequence, the gnathic 

 index which is obtained from these measurements is practically the same in the 

 two groups. 



The mean value of the basi-nasal length is only about 1 mm. less in the West 

 Scottish male series of 405 than it is in Turner's group. Table V shows the skulls 

 classified according to the gnathic index : — 



Table V. 



Class." 



West Scottish Series. 



Turner's Series. 



No. 



Per cent. 



No. 



Per cent. 



Orthognathous (below 98) 

 Mesognathous (98-103) 

 Prognathous (103 and upwards). 



308 



84 



7 



77-2 

 21 

 17 



72 



24 



1 



74-22 



24-74 



1-03 



The near approach to equality between these proportions in the different classes 

 and those in the scries under examination is notable, and confirms Turner's con- 

 clusion that the Scottish skulls are characterised by an almost complete absence of 

 prognathism. 



Skulls are classified into three groups according to the value of their orbital 

 index as follows. Tabic VI shows the two series classified according to the value 

 of the index. 



