1898-99.] Dr Hepburn on Improved Form of Craniometer. 601 
An Improved Form of Craniometer for the Segmen- 
tation of the Transverse, Vertical, and Antero- 
Posterior Diameters of the Cranium. By David 
Hepburn, M.D., C.M., Lecturer on Regional Anatomy in 
the University of Edinburgh. (With a Plate.) 
(Read July 3, 1899.) 
Introduction. — All craniologists are familiar with the form of 
craniometer or calliper-compasses at present employed for the 
purpose of ascertaining the various diameters of the cranial box, 
and they know that these measurements represent certain facts in 
connection with the breadth, height, and length of the skull as 
applicable to a number of accepted fixed points upon the surface of 
the cranium. In effect these diameters are the direct lengths 
between two points upon an arched surface, i.e ., they are the 
chords of certain arcs, and by the use of the measuring tape we 
may ascertain the relative proportions between the arc and the 
chord which subtends it. When several bones contribute to the 
formation of the arc we may readily determine the relative pro- 
portions between each section of the arc (or the chord of each 
section) and the chord of the entire arc, but it is a much more 
difficult matter to segment the chord of the entire arc in terms of 
perpendiculars prolonged to it from definite points upon the arc. 
For example, by callipers we obtain the glabello-occipital length 
or chord of the great longitudinal arc, and by measuring tape we 
may ascertain the frontal, parietal, and supra-inial sections of this 
arc, but we do not thereby segment the chord of the arc by 
perpendiculars prolonged to it from the bregma and the lambda. 
Again, such important transverse diameters of the skull as the 
minimum frontal, Stephanie, greatest parieto-squamous, and 
asterionic, are recorded without reference to their proportions on 
opposite sides of the mesial plane, while the almost constant 
visible asymmetry of the skull shows that the mesial plane does 
not necessarily bisect these diameters. Further, the basi- 
bregmatic height might he segmented in terms of a point selected 
VOL. XXII. 10/11/99 2 Q 
