MEASUKEMENTS AND INDICES. 287 



projection of the lower part of the face. The larger angle is the concomitant of a more vertical 

 profile. The degree of projection, of the maxilla in the macerated cranium is most commonly 

 expressed by employing the gnathic or alveolar index of Flower. This records the relative 

 proportions of the basi-alveolar and basi-nasal lengths, the latter being regarded as = 100, 

 thus 



Basi-alveolar length x 100 



= Gnathic index. 

 Basi-nasal length 



The results are conveniently grouped into three classes : 



Orthognathous, index below 98 : including mixed Europeans, ancient Egyptians, etc. 

 Mesognathous, index from 98 to 103 : Chinese, Japanese, Eskimo, Polynesians (mixed). 

 Prognathous, index above 103 : Tasmanians, Australians, Melanesians, various African 

 Negroes. 



Unfortunately, however, little reliance can be placed on the results obtained by this method, 

 since it takes no account of the proportion of the third or facial side of the gnathic triangle. 

 For a further discussion of this matter see Thomson and Maclver, Races of the Thebaid (Oxford : 

 Clarendon Press, 1905). 



The form of the piriform aperture in the macerated skull is of much value from an ethnic 

 standpoint, as it is so intimately associated with the shape of the nose in the living. The 

 greatest width of the aperture is compared with the nasal height (measured from the nasion 

 to the lower border of the aperture) and the nasal index is thus determined : 



Nasal width x 100 . 



= Nasal index. 

 Nasal height 



Skulls are 



Leptorhine, with a nasal index below 48 : as in mixed Europeans, ancient Egyptians, 



American Indians, etc. 



Mesorhine, with an index ranging from 48 to 53 : as in Chinese, Japanese, Malays, etc. 

 Platyrhine, with an index above 53 : as in Australians, Negroes, Kaffirs, Zulus, etc. 



The form of the orbit varies considerably in different races, but is of much less value from the 

 standpoint of classification. The orbital index expresses the proportion of the orbital height to 

 the orbital width, and is obtained by the following formula : 



Orbital height xlOO 



Orbital width 



The orbital height is the distance between the upper and lower margins of the orbit at the 

 middle ; whilst the orbital width is measured from a point where the ridge which forms the 

 posterior boundary of the lacrimal groove meets the fronto-lacrimal suture (Flower), or from 

 the dacryon (Broca) to the most distant point from these on the anterior edge of the lateral 

 border of the orbit. 



The form of the orbital aperture is referred to as 



Megaseme, if the index be over 89 ; 

 Mesoseme, if the index be between 89 and 84 ; 

 Microseme, if the index be below 84. 



The variations met with in the form of the palate and dentary arcade may be expressed by 

 the palato-maxillary index of Flower. The length is measured from the alveolar point to a 

 line drawn across the posterior borders of the maxillae, whilst the width is taken between 

 the outer borders of the alveolar arch immediately above the middle of the second molar 

 tooth. To obtain the index, the following formula is employed : 



Palato-maxillary width x 100 = p alato . maxillary index . 



Palato-maxillary length 



For purposes of classification Turner has introduced the following terms : 



Dolichuranic, index below 110. 

 Mesuranic, index between 110 and 115. 

 Brachyuranic, index above 115. 



As is elsewhere stated the size of the teeth has an important influence on the architecture of 

 the skull. Considered from a racial standpoint, the relative size of the teeth to the length of 

 the cranio-facial axis has been found by Flower to be a character of much value. The dental 

 length is taken by measuring the distance between the anterior surface of the first premolar and 

 the posterior surface of the third molar of the upper jaw. 



To obtain the dental index the following formula is used : 



Dental length x 100 _ pental index 

 Basi-nasal length 



