DE. J. CLELAND ON THE VARIATIONS OF THE HUMAN SKULL. 
125 
ancl in two to 5‘3 ; in the remainder it varies from 4‘9 to 5-2, while we have already 
seen that in the child ten years old it reaches 5T. It appears from this that the addi- 
tional growth by which the base-line in the male comes to exceed that found in the 
female takes place after the age mentioned. It might therefore be naturally supposed, 
as occurred to the writer, that the facts which have now been detailed are mere results 
of greater development of the frontal sinus in the adult male than in the female and 
child, and in the savage than in civilized races ; but this is not the case ; for we shall 
find that though development of the frontal sinus does add to the base-line, growth of 
the base of the skull from the front of the foramen magnum forwards to the level of the 
foramina optica plays a much greater part in the addition which takes place. 
Regions of the base . — According to the system of measurement pursued in the present 
inquiry, the base of the skull is represented by three lines, the middle one of which, the 
foramino-optic line, corresponds pretty nearly with the ‘ basicranial axis ’ of Huxley ; 
while the hindmost displays the length of the foramen magnum, and the foremost the 
length of the orbit ; the length of the base-line varying according to the length of these 
distances, and the angles at which they are placed one to another. 
Foramen magnum (General Table, column 25). — This is the region of the base which 
presents least characteristic variation in length. It usually measures from 1*4 to 1*5. 
The extremes met with are T25 and 1-70. Little or no distinction of a national 
character is discoverable in its variations ; and although skulls which have a markedly 
long base-line sometimes owe the peculiarity in a small degree to the length of this 
foramen, as Esquimaux 77 and Kafir 69, there are other skulls, such as 23 and 56, and 
the infant skull 11, which combine a long foramen magnum with a short base-line. The 
proportion borne by the foramen magnum to the base-line does not appear to undergo 
any constant alteration in the passage from infancy to adult age. 
Orbital length (General Table, column 27). — This measurement likewise has the 
same proportion to the base-line at birth as in the adult. In the six-years-old as well 
as in the twelve-years-old child it is of a length which might be permanent ; in the 
adult male it is slightly but distinctly greater than in the female. The national varia- 
tions are well worthy of remark. If influenced by the belief that large development of 
the frontal part of the skull accompanies intellectual capacity, we might expect to find 
a greater orbital length in civilized than in savage nations. But this is not the case. 
Lucae, in his comparison of European and Australian skulls, pointed out that the floor of 
the anterior fossa of the skull was quite as well developed in the latter as in the former * ; 
and this observation is quite in harmony with the present measurements, although un 
fortunately he has accompanied it with the hasty remark, not borne out by his drawings, 
that the Australian development is defective in the upper part of the frontal region. 
In the meantime, however, let us consider simply the orbital length. The range of 
its variation in the great majority of skulls is from TS to 2T. In the Australian, Negro, 
and Kafir the average is high, while in the French and German it is shorter than in any 
* Lucae, op. cit. p. 40. 
MDCCCLXX. 
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