DE. J. CLELAND OX THE YAEIATIOXS OF TTIE HUMAN SKULL. 
131 
Length of arc of the different portions of the arch (General Table, columns 3, 4, 5, 
9, 10). Young skulls . — It is well known that in early life the frontal and occipital 
parts of the skull are smaller as compared with the parietal than in the adult*; and in 
accordance with this an examination of the Table shows that in foetal life, infancy, and 
childhood, the length of the frontal and of the occipital portion of the arch both bear, as 
a general rule, a smaller proportion to the length of the parietal portion than they do in 
the adult. It is not, however, to be supposed that the parietal has a predominance over 
the frontal and occipital region from the first, and that these grow proportionally larger 
in an equable manner ; for setting aside the consideration that in the young embryo the 
wall covering the posterior cerebral vesicle is much larger than what is afterwards to 
become the parietal and frontal part of the cranium, and confining attention to the 
measurements in the Table, it appears that from the fourth month of foetal life till birth, 
while the disparity between the parietal and occipital regions is diminishing, the disparity 
between the parietal and frontal is increasing. Five of the six foetal skulls examined have 
the occipital smaller in proportion to the parietal than it is in the skulls of the new-born 
infants, and four out of the five skulls of infants have the frontal smaller in proportion 
to the parietal than it is in the foetal skull. The conclusion from this is that the pari- 
etal has grown more than the frontal, and the occipital more than the parietal in the 
later months of foetal life. But after birth the frontal, which has been for a time the 
slowest growing region, begins to expand most rapidly of the three, while the occipital 
region still continues to expand more rapidly than the parietal. This is indicated in 
the General Table by the children’s and adult skulls having the proportionate length of 
the frontal, as compared with the parietal region, much higher than the new-born infants, 
and likewise having the proportion of the occipital to the parietal region higher than 
the infant skulls, though not greatly so. 
It further appears, on estimating the percentage of the whole arch formed by each 
region respectively, that already in the youngest foetus examined the frontal region forms 
as high a proportion of the whole arch as it does in the adult, but that at birth the pro- 
portion is temporarily diminished ; while the percentage belonging to the parietal region 
goes’ on diminishing, and the percentage belonging to the occipital goes on slightly 
increasing, from the youngest foetus examined till the adult skulls are reachedf. No 
doubt the result is obscured by the large amount of individual variation which exists in 
different skulls, and to arrive at a precise estimate of the average extent of each region 
at different periods of development would probably require the examination of a large 
number of skulls; but a careful review of the figures justifies the statement now 
made. 
Taking a survey of the growth of the cranium from the earliest period, the following 
account is probably correct. At first, in the early embryo, the occipital region is much 
* Huschke, ‘ Schadel, Him, und Seele,’ p. 46. 
t The percentage which each portion of the arch forms of file whole, though calculated, is omitted from the 
General Table, to prevent unnecessary multiplication of figures. 
