DESCRIPTION OF FIGURES OF SKULLS. 563 



index;' and a 'maxillary^ index,' giving the relations of the basi- 

 cranial line to a line passing from the middle of the anterior 

 border of the foramen magnum, the ' basion ' of Broea, to the nasal 

 spine. The value of these measurements is beyond question ; but 

 as the important point in each of these eases is simply one of 

 greater or less magnitude, oscillating within narrow limits^ the in- 

 convenience of additional statements of proportion is not counter- 

 balanced by much corresponding advantage. I have, however, 

 given one measurement of proportions in addition to the ' Cephalic 

 Index ;' and this, which I have called the ' Antero-posterior Index/ 

 gives the relation which is held to the extreme length of the skull 

 by that part of the extreme length which lies anteriorly to the 

 auditory foramen. The extreme length being taken^ as above 

 described, it is divided into an anterior and a posterior segment 

 by a line passing as a tangent to the anterior border of the audi- 

 tory meatus, and prolonged so as to cut the line of extreme length 

 at right angles. The proportions between these segments may be 

 very readily obtained by fitting an indicator to one of the longer 

 sides of M. Broca's '■cadre a maxhna'^^ and, when the instrument 

 is so applied as to take the extreme length, adjusting the indi- 

 cator so as to run as a tangent to the anterior edge of the auditory 

 meatus. The vertical line thus obtained falls always some way 

 behind the junction of the coronal and sagittal sutures ; but though 

 it fails thus to coincide with the vertical line chosen for placing 

 the skull in for the purpose of drawings it does coincide very nearly 

 with the line which might be drawn across the external surface of 

 the cerebral hemisphere for limiting posteriorly the area which 

 is most favourably conditioned as to irrigation with arterialised 

 blood. The segments therefore into which it divides the line of 

 extreme length may be held to correspond respectively to more 

 and to less favourably nourished and actively operating segments 

 of the cerebral hemispheres, and the statement of their relative 

 proportions as expressed in the 'Antero-posterior Index ' assumes 

 considerable importance. 



The indications as to prognathism and its absence furnished by 

 the ' maxillary index ' of Virchow and the ' gnathic index ' of Busk 

 (Journal Anthrop. Instit. London, Jan. 1874, p. 496) are both 



' Virchow, Archiv ftir Anthropologie, vol. iv. p. 63, 1870. 



^ For description of this useful instrument, see Bulletin Soc. Anthrop. Pari.s, 

 lom. iv. (2*^® Serie'*, pp. 101-104, 1869 ; or Meinoires d'Anthropologie par Paul Broca, 

 torn. i. p. 152, 1871. 



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