DR. J. CLELAND ON THE VARIATIONS OE THE HUMAN SKULL. 
143 
measures from the fronto-parietal suture in the mesial plane to the front of the foramen 
magnum*, thus making the line of height agree as nearly as possible with that which 
he has adopted from Mr. BusKf as expressing vertical direction, namely, a line from the 
fronto-parietal suture to between the openings of the ears. The present writer, however, 
appreciating, as Mr. Huxley has also done, that some skulls appear to stand vertically 
over the base while others slope upwards and backwards, has sought for a line the incli- 
nation of which will vary with the slope of the skull ; and believing that the best cri- 
terion of that slope is the direction of the line of frontal depth, he has measured the 
height of the skull by a line passing upwards from the front of the foramen magnum 
parallel to the frontal depth. This line has the disadvantage in the present inquiry that 
its upper extremity does not exactly correspond with any of the measured points laid 
down in the diagrams, but the possibility of error from this source has been found to be 
very slight. 
Proportion of height to f rontal depth (column 74). — The proportion which the height 
measured as now stated bears to the frontal depth varies very much in different indi- 
viduals ; but, like steepness and levelness of the base, on which to some extent it is 
dependent, it is not a matter apparently of national distinction. It may, however, be 
remarked that those nationalities in which the parietal depth was great in proportion 
to the occipital, occipito-parietal, and frontal depths, have also a high proportion of 
height to frontal depth. 
The question arises, how far excess of the line of height over the line of frontal depth 
depends on rise of the roof of the skull, and how far on sinking of the base ; and this may 
be determined by examining the relation borne to the line of orbital length by the line 
uniting the midparietal and fronto-parietal points. This line, which is always cut by 
the line of height, sometimes, as compared with the line of orbital length, rises five or six 
degrees as it passes backwards, sometimes falls as much, but on an average and much 
more frequently is parallel with it in the adult. In the infant it rises greatly and most 
characteristically as it passes backwards ; when the gravitation changes set in, they tend 
to make it fall; and in the compressed American skulls 95 and 96, and even in the 
French skull 27, which has probably been accidentally compressed by a head-dress in 
the manner described by Gosse J, it rises enormously behind, as it does in no natural 
adult form. Thus it appears that in the normal adult skull the excess of the line of 
height over the frontal depth is dependent almost entirely on sinking of the base, but 
that in the infant and in artificially deformed skulls it depends in great part on rise of 
the roof. The conditions in the base of the skull which increase the excess of the line 
of height over the frontal depth are length of the foramino-optic line and greatness of 
the angle between that line and the line of frontal depth, which of course involves 
steepness of the base. Also, the proportional excess is increased by absolute shortness 
* Journal of Anatomy and Physiology, November 1866. 
t Natural-History Review, October 1862. 
± Deformations artrflcielles du Crane : Paris, 1855. 
u 2 
