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Mr. Victor Horsley—Cranio-Cerebral Topography.

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ten units, lie obtained lines which divided the head into proportionate
amounts of a perfectly relative kind. His results in consequence are
particularly valuable.

He found that in the mesial plane the upper end of the fissure of
Rolando was situated as follows :—

In skulls of 18 cm. and more in mesial length, the upper end of the
Rolandic fissure was at a point of 56*5 per cent, of the mesial arc measuring
from the glabella; while for skulls below 18 cm. it is less, namely, 55 per
cent, of the same arc. As a general average Miiller finally obtained
55 per cent, as the most accurate result. Reid's method of erecting a
perpendicular on a basal-orbital inial line, at a point which he names
" the posterior border of the mastoid process," is often quoted as a relative
measurement, but it has no claim to be considered as an accurate guide,
since the posterior border of the mastoid process has an antero-posterior
extent of some 2 cm., and consequently is by no means a definite point.
Moreover, the whole procedure of erecting verticals on base lines to
localize what lies at the vertex is so obviously open to such gross error
that this and similar methods ought to be discarded entirely.

Le Fort states that, contrary to Hare and the majority of English and
American observers, he has not found the upper end of the Rolandic
fissure at approximately #557 of the sagittal arc length, but at a mean
distance of '532. Curiously, in contrast to what he states earlier in his
work, he goes on to say that the distance is even less in dolichocephalic
heads, e.g. *520, and more in brachycephalic, viz. '545.

Debierre found, as all preceding him, that the upper end of the fissure is
measured from the front 55 per cent, of the glabella-inion arc.

Giacomini employs a special method. He first takes the maximal
transverse diameter of the cranium ; then having drawn the usual sagittal
line, he connects the two extremities of the transverse diameter by a line
drawn at right angles to the mesial plane. The line connecting the two
extremities of the maximal diameter must, of course, cut the fissure of
Rolando at a certain point and at a certain angle. Where the Rolandic
line cuts the transverse diameter line, and makes an angle with the latter,
he finds by measurement that on the average that angle varies from 30 to