Freiburger historische Bestände - digital

330

Cunningham Memoirs.

On estimating the possible error in the localization of the lower end of
the fissure if the angle were not properly determined,* I found it amounted
to about 2 mm. for each degree; consequently, it is possible, in using a
cyrtometer without the correction about to be proposed, to fall into an
error of 2 cm., or more than the breadth of an ascending gyrus, a very
serious mischance. To remedy this I further improved, in 1890, on
Wilson's modification of my instrument, by first fixing a button on the
end of the mesial band, so that the commencement of the longitudinal
graduation should commence exactly at the nasal suture or nasion, and not
at the glabella. It is unfortunate that by agreement of anthropologists the
glabella was fixed upon as the point limiting anteriorly the cranium in
maximal length, since its position is not definite on the mesial plane.
Zernoff, who discards, for this reason, the glabella as a fixed point, states
that he takes " the frontal point of Broca." It is difficult to know what he
means by this statement, as Broca never speaks of a frontal point. It is
clearly not the ophryon. There remains, therefore, only the nasion,
and the instruction for employing his encephalometer bears this out.
I have followed Thane in measuring the mesial length from the
naso-frontal suture (nasion) as giving the final cranial limit, and cannot
regard the employment of the glabella as a satisfactory starting-point.
The mesial band can be easily steadied and fixed in position by employing
the brow-band, as introduced by Wilson. The total distance
between the nasion and the inion having been accurately read off in
centimetres and millimetres, it is divided in half, and one centimetre
(Thane's point modified) added to the result. An arc, with an adjustable
(Eolandic) arm fixed by a screw, is now slid on to the mesial band, an
index being fixed above the arc, and distant 6 cm. from the axis about
which the Eolandic arm turns, marking finally the spot at which the
upper end of the fissure lies. The point of the index (put for clearness

* Poirier, after measuring the angle in fifty hemispheres, has found (1891) the angle varied
within limits of considerable extent.

f Debierre has recently constructed a goniometer for the same purpose, and states that,
from certain measurements, he finds the average Eolandic angle to be 65°. Mine is made by
Mr. Hawkesley, 357, Oxford-street, London.