DR. J. CLELAND ON THE VARIATIONS OE THE HUMAN SKULL. 
149 
ceased, the surfaces above and below the lateral ridges are rounded out in well-tilled 
skulls ; but in ill-filled savage skulls that rounding-out fails to take place, and thus 
there is the more prominent mesial ridge and the higher position of the point of greatest 
breadth. The rounding-out of the sides of the skull which occurs from the latest 
expansion of the brain is followed by that which is brought about by gravitation, as 
already described, and thus the increase in breadth does not necessarily cease on arrival 
at adult age, but may continue through life. Another position of the point of greatest 
breadth, indicating a more degraded form than that in which it is placed high on the 
parietal, has only been met with in one skull in the list, that of the Idiot. In that skull 
the greatest breadth is between the mastoid processes, as it is in the Gorilla and Chim- 
panzee, a condition resulting from the poor development of the arch of the skull. 
Radial measurements and position of the ear (columns 47 to 63, and 69 and 70). — 
As it is impossible on the living subject to obtain measurements extending from points 
in the arch to points in the base, it would often be convenient to obtain information as 
to cranial configuration by means of measurements radiating from the external auditory 
meatus, like those proposed by Mr. Busk*. In the present instance the postauricular 
depression has been chosen for convenience instead of the centre of the auditory meatus 
as the starting-point, and the radius to the midparietal point has been chosen as a 
standard with which the other radii are compared. 
The radial measurements serve well to display the differences between the infantile 
and the adult form of skull. In the infant the radii in front of the midparietal radius 
bear a smaller proportion to that radius than they do in the adult, and the difference 
is greatest in those furthest forward. Thus the proportional distance of the fronto-nasal 
suture from the postauricular depression, counting the midparietal radius as 100, is 70, 
and in the adult European about 83. To understand the significance of this difference, 
let the midparietal radius be estimated at 5 inches in the adult, and let the infant’s 
head be magnified sufficiently to bring that radius to the same length in it, then the 
distance to the fronto-nasal suture in the adult will be 4T5, and in the infant 3'5, or 
•65 of an inch less than in the adult. Turning to the parts behind the midparietal 
point, it may be observed that the proportional distance of the occipitoparietal point 
from the ear is as great as in the Irish and Scotch skulls, and greater than in the French 
and German ; the distance of the midoccipital point is slightly less than in the Irish 
phocephalic, of which he describes various examples, the youngest of them being the cranium of a foetus, re- 
marks on the deficiency of height in the scaphocephalic skull, and asks why the compensatory growth re- 
quired in consequence of the want of breadth does not take place upwards as well as in the longitudinal direc- 
tion. The answer to that question may be gathered from the text. The height of the parietal region of the 
skull above the parietal eminences is obtained by the growth of the inner margins of the parietals, and when 
synostosis of those margins occurs, or when, as may be the case in some instances, there is but a single centre 
of ossification from which one ‘ biparietal’ bone takes origin, not only is this source of upward growth lost, but 
the parts corresponding to the portions below the eminences of normal parietals are placed in a sloped instead 
of a vertical position. 
* Natural-History Review, October 1862. 
MDCCCLXX. X 
