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180

Cunningham Memoirs.

hemisphere, but notwithstanding this the upper end of the fissure of
Rolando has precisely the same relative position in both. The measurements
which I have made of adult cerebral hemispheres have led me to
very nearly the same results. In forty-five right hemispheres the average
upper fronto-Rolandic index was 53'1 ; in thirty-seven left hemispheres
the average index was 53-7. The difference is trifling, and therefore I
believe that in the two hemispheres the upper end of the fissure of Rolando
virtually holds the same relative position.

V. Relation of the Fissure of Rolando to the Cranial Vault.—The

position of the fissure of Rolando in relation to the coronal suture at different
periods of growth must next engage our attention. This is expressed
in the series of upper and lower corono-Rolandic indices in the following
Table :—

Topography of the Fissure of Rolando with reference to the Coronal Suture.
Mesial Length of the Hemisphere = 100 ; Lateral Length of the Hemisphere = 100.

Period of Development.

Number of
Hemispheres
Examined.

Upper
Corono-Rolandic
Indices.

Lower
Corono-Rolandic
Indices.

Life.

5J to 6^- months,

5

9-9

5-6

uterine

to 7-J- months,
7£ to months,

6
10

11-9
17-2

3-6
9-0

Intra

Full-time foetus,

11

18-2

10-7

Life.

3 months,

5

18-6

12-8J

6 months,

3

14-4

8-6

nterine

12 months,
4 to 5 years, .

2
12

13-6
16-5

5-1
11-3



11 to 15 years, .

3

16-1

8-8



Adults, ....

15

16-7

12-9

We have seen that the position of the fissure of Rolando on the surface
of the brain is subject to very slight alterations, and that in all probability