602 Proceedings of Royal Society of Edinburgh. [sess. 
upon the lateral aspect of the skull, so as to provide an approximate 
representation of the proportions of this diameter which pertain 
respectively to the cerebrum and cerebellum. 
Doubtless opinions may differ as to the value of recording 
figures which express the segmentation of the different diameters 
of the skull in terms of certain fixed points situated in their arcs, 
but that they have not already been recorded is in all probability 
due to the difficulty of obtaining them without having recourse 
to trigonometric calculations, a method which has not attracted 
the craniologist. Various efforts have been made to obtain this 
kind of information. Thus, an instrument was devised for the 
purpose of measuring radii drawn from an inter-aural axis to 
different points upon the surface of the skull, but the results have 
not warranted its extended use. Again, Sir William Turner,* by 
bisecting the skull and drawing radii from the basion to different 
points upon the surface of the skull, as well as by raising a perpen- 
dicular to the plane of the foramen magnum from the basion to the 
vertex, obtained much valuable information, but the extension 
of this method entailed serious damage to each skull which was 
bisected. 
Professor Cleland f has also followed a plan which was associated 
with bisection of the skull, and had for its object the calculation 
of the chords and angles connected with each section of the great 
longitudinal arch, as well as the distance of various points upon 
the arch from the base of the skull. 
As the result of a conversation with Dr Waterston, Demonstrator 
of Anatomy in the University of Edinburgh, my attention was 
directed to the possibility of solving the problem without the 
necessity of elaborate calculations, and I have accordingly devised 
a modified form of craniometer which overcomes the former 
difficulties, and by means of which cranial diameters may be 
segmented by perpendiculars prolonged from fixed points upon 
the surface of the skull. Moreover, besides being easily per- 
formed, this operation does not necessitate any damage of the 
* Turner. Chall . Rep., “Human Crania,” Part xxix.. 1884. 
t Cleland, “An Inquiry into the Variations of the Human Skull, par- 
ticularly in the Antero-Posterior Direction,” Phil. Trans., 1870, yol. clx. 
pp. 117-175. 
