i6 



THE VARIETIES OF THE HUMAN SPECIES. 



Let AA' be the antero-posterior diameter of a cranium, BB' 

 the greatest transverse; it is evident that, given the norma verti- 

 calis with such diameters and with the greatest transverse at the 

 conjunction of the hne BB', this norma verticalis takes a particu- 

 lar form on account of the curves which surround the two diame- 

 ters. This Hne or curve, which surrounds them, is called X. If 

 the greatest transverse is placed back and is made to coincide with 

 the line CC, the curve will be modified and will no longer be X 

 but Y. That will be equally true if the transverse diameter is 

 placed still further back at DD', EE', FF'; then we shall have a 

 third curve Z, a fourth, a fifth, «, that is, we shall have as many 

 different vertical curves on account of the changing of the diame- 

 ter of the width, as the index causes ; that is, the relation between 

 the length and the width will be the same. 



From this it may be judged how much more will the norma 

 verticalis vary if the form of the curve circumscribing the two 

 diameters be modified in other ways, that is, by the frontal width, 

 by the occipital form, and so on. If we also add the lateral curves, 

 those posterior and anterior, which serve to show the form of this 

 irregular body, we shall easily be convinced that the cephalic and 

 vertical index cannot give the cranial form. That is why I have 

 above stated that the expression of Virchow, "The form of the 



