162 
DR. J. CLELAND OX THE VARIATIONS' OF THE HUMAN SKULL. 
Deviation from the assumed horizontal plane 
Of the foramen magnum. 
Of the line of 
orbital length. 
4 Infants 
6-2 
O 
11-5 
7 Children 
7- 
3 
5-5 
Males. 
Females. 
Males. 
Females. 
Hindoo 
O 
7-6 
German 
O 
5*8 
O 
4 
Esquimaux 
8‘5 
Hindoo 
7 
Australian 
9 
Australian 
10 
Kafir 
10 
O 
20 
Irish 
10-8 
4-3 
Greek 
10-7 
Scotch 
11-4 
8 
German 
13 
8-6 
French 
12-8 
3-6 
Negro 
13-4 
8*5 
Greek 
13-5 
Scotch 
13-6 
11 
Negro 
16*4 
9-5 
French 
14-6 
11-3 
Esquimaux 
17-5 
Irish 
15-5 
11-6 
Kanaka 
19 
8 
Kanaka 
16 
17 
Kafir 
20-3 
14 
After the greatest adult male rotation backwards of the skull has been accomplished, 
a reverse change may take place as a feature of old-age degeneration. The condyles 
in that case become flatter, and the head, in consequence of this, is necessarily rotated 
forwards ; for it may be safely assumed that no elevation of the floor of the facets of the 
atlas takes place, by which alone such rotation could be prevented. That such an old- 
age degeneration actually occurs can scarcely be denied, but among the skulls measured 
there are only three well-marked examples of it, namely, the old Scotch skull 40, the 
German 28, and the Greek 47 ; they are, however, really good examples. The first two 
exhibit in a marked manner all the gravitation changes of form ; the third does not 
exhibit those changes in a typical manner, as it has a nearly vertical forehead which can 
scarcely be imagined to have fallen much backwards ; but probably it has undergone a 
partial change like the German 29, which appears to have enlarged its foramino-basilar 
angle by the weighing down of the back part of the cranium and its contents. The 
tendency of the gravitation changes is to throw more of the weight of the brain and skull 
behind the condyles; and this, together with absorption of the substance of the jaws, 
and that enlargement of the air-sinuses at the expense of osseous tissue which goes on in 
old age even after the entrances into the sinuses are blocked up, makes the fore part of 
the head lighter ; and thus the rotation forwards by flattening of the condyles tends to 
preserve the balance. This flattening of the condyles is in harmony with the general 
tendency in old age to absorption of osseous matter, especially cancellated tissue — a ten- 
dency which is shown in the skull, not only in the extension of the air-sinuses, but in 
thinning of the bone opposite the inferior occipital fossse, and in the squamous portions 
of the temporals. Indeed the much remarked thickening of the skull in old age seems 
to be confined to those parts which are subjected to increased exposure by baldness. 
Applications of the foregoing remarks to artistic anatomy . — The foregoing remarks 
tend to explain the superficial appearances seen in the form of the head at different 
ages and in the two sexes, as well as in individuals ; but, in applying them, it must be 
