Orientation points which approach either the assumed vertical or horizontal. Unfortunately the
obtain a true adoption of Huxley’s system involves making a mesial section of the skull, and though
the^ro^ec- *n manY instances there may be no objection to such procedure, yet it must be borne
tionPofthe" in mind that oftentimes, when dealing with skulls of great age, it is difficult enough
to preserve the crumbling remains intact without proceeding to apply the saw.
Cleland, in 1870*, following on the same lines, proposed a modification of the above
method. His base line, which extends from the opisthion to the nasion, included three
parts— a middle part corresponding pretty nearly with Huxley’s ‘ basi-cranial axis,’ an
anterior portion corresponding to the length of the orbit, and a posterior including the
length of the foramen magnum. In dealing with Cleland’s base it was necessary to note
the angle formed by each of the above divisions with the others. There, again, in order
to do so it was necessary to bisect the skull longitudinally.
Owing to the great morphological importance of the basi-cranial axis it seemed
to us of the utmost advantage to utilize this part of the cranium as a base on which
to compare the development and form of the brain capsule dorsally, as well as the
variations in shape of the facial skeleton ventrally.
1 P h il. T ra n s. 1870.
To do so, however, without entailing the division of the skull, necessitated the
addition of portion of the ethmo-vomerine region to the basi-cranial axis, the two combined obtain a true
corresponding to the entire length of the basi-nasal line. With the view of determining the™rojec-
whether such a method was likely to prove useful certain observations were made. fi°e°fhiS
In the first instance, thirty-eight skulls were oriented in the now generally accepted
Frankfort-Munich plane; when so
disposed, the angle formed by the
basi-nasal line with the horizontal
plane was carefully measured by
means of the craniophore, a figure of
which is here given1 (Fig. 3). The
angle measured was found to vary
from 220 to 340. As has been previously
stated, the thirty-eight skulls
were selected because they displayed
every variety of orbital form, and a
variation with a range of 13 mm.
between the levels of the inferior
orbital margin and the nasion. Consequently
there was a source of error
in the orientation in the Frankfort-
Munich plane with a possible range of 13 mm. A comparison of the results obtained2
proved that as a rule the largest angles were associated with the skulls in which the
inferior orbital margins were farthest removed from the level of the nasion, and conversely
the narrowest angles were met with in those skulls in which the distance between the
levels of the inferior orbital margin and nasion was reduced. Similarly the angle tended
to widen with the numerical increase in the value of the orbital index, in other words, a
skull which was megaseme, when oriented in the Frankfort-Munich plane, usually displayed
a wider angle between the basi-nasal line and the horizontal than one which was microseme
(see Fig. 4).
As a result of these observations,
it was decided to adopt 270 as the
average angle formed by the basi-nasal
line with the horizontal. To orient the
skull in this position all that is necessary
is to place the skull on the craniophore
(Fig. 3) and raise the vertical plate until
an angle of 2 70 is reached on the scale on
the arc. Another method (Fig. 5), which
does not involve the use of such an apparatus,
is to construct a framework sufficiently
large to enclose a cranium; the sides of this frame are cut so as to form wedges
the angles of which are each 270. A thin metal plate bb of the same width as the
inside of the frame is taken, and to the mid line across it is affixed a smaller wedge a
with a similar angle of 27°* The frame is now so placed that the edges of the wedges fall
1 F o r fuller description o f this instrument, see Appendix, p. 123. 2 See Appendix, p. 124.