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Mr. Victor Horsley—Cranio-Cerebral Topography.

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2. From the fifth year to adolescence the distance between the fissure
and the lambda is notably reduced.

3. In adult life the fissure lies in the large majority of cases just in front
of the lambda. (Relative position 2*9 ; mesial length of hemisphere = 100 ;
absolute measurements averaging about 5 mm.)

4. In adult life the fissure not infrequently coincides with the lambda,
and very rarely lies behind it. According to Passet the fissure in the male
is usually further forward than in the female. (Of. Altoukhoff.)

IV. Topography of Furrows.—Class II. Those subdividing Lobes:—

(A) Frontal Lobe.

(B) Parietal Lobe.
(67) Occipital Lobe.
(D) Temporal Lobe.

(A) Frontal Lobe—The Topography of the /Subordinate Sulci.— The
numerous sulci on the frontal lobe will now be dealt with under the names
adopted by Professor Cunningham in Chapter V., page 244.

Sulcus Prcecentralis Inferior.—Of these the most important is the sulcus
prsecentralis inferior, or, as it is more usually termed, the prsecentral sulcus
simply. Around the various portions of this sulcus are grouped most
important foci of representation of various regions of the body.

For the present purpose we have to consider—

(a) The vertical stem.

(b) The focus of branching.

(a) The vertical stem lies, in the large majority of cases, behind the
coronal suture in its lower half. In a small number of cases it coincides
with the suture, but in most instances is set some millimetres posteriorly to
the bony line in question.

Professor Cunningham has shown that the inferior prsecentral sulcus,
like the Rolandic fissure, is remarkably constant in its relative position to
the rest of the hemisphere, the index being 37'8 when the maximal length

ROYAL IEISH ACADEMY.-CUNNINGHAM MEMOIRS, NO. Til. [43]