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Me. Victor Horsley—Cranio-Cerebral Topography.

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accuracy for guiding the vertical lines; but the plan cannot be accepted as
an absolutely reliable indication of the lower end of the Eolandic fissure.

(2) The determination of the lotver end of the fissure of Rolando by measurement
of the distances between it and the surrounding sutures.

(a) Relative Measurements.—Midler (yid. p. 324) found that, by his
important method of vertical and horizontal arcs, he could localize the
lower end of Eolando as follows:—

In skulls of a sagittal length of 18 cm. and over, the lower end of the
Eolandic fissure = 45'5 to 45 per cent, of the horizontal arc measured from
the glabella.

In skulls of a sagittal length of less than 18 cm. the percentage was
greater—viz. 46 per cent, of the arc. The general average finally obtained
by Miiller was 42 to 43 per cent.

Eeid's method involves the following procedures:—

(1) Drawing a base line from the inferior border of the orbit to the
centre of the external auditory meatus.

(2) Erection of a vertical line on (1), starting from the prae-auricular
depression, and continued up to the line marking the posterior limb of the
fissure of Sylvius. Where these two latter intersect is the position of the
lower end of the fissure.

Apart from the fact that the Eolandic fissure terminates in the large
majority of cases (see p. 163) above the Sylvian fissure, this method is
disadvantageous, from the fact that it depends on a base line which is
always fallacious, and the anterior end of which is not in relation with the
cranium, but with the facial bones (see also p. 307.)

Makins and Anderson employ a combination of relative and absolute
measurement, and conclude that the lower end of the Eolandic Fissure lies
between the intersection of a line joining the mid-sagittal point* and preauricular
fossa, with one (" squamosal") joining the external angular process
of the frontal bone and the junction of the middle and lower thirds of the
former line (" frontal"), and a point three-eighths of an inch in front of such
intersection. It is clear that this rather more arbitrary method shares
many of the errors involved in Eeid's plan.

* Found by halving the distance between the glabella and inion.