Freiburger historische Bestände - digital

192

Cunningham Memoirs.

IX. Summary.—1. Eolando was not the first observer who described
the fissure which bears his name, and it was only through an accidental
circumstance that his name became associated with it.

2. In 60 per cent, of the brains examined the upper end of the fissure
of Rolando turned over the mesial border of the hemisphere, and appeared
on the mesial surface; in 19 per cent, its lower end presented a shallow
connexion with the fissure of Sylvius.

3. This latter connexion was established by means of the inferior transverse
sulcus of Eberstaller.

4. The fissure of Rolando is developed in two pieces. Its lower
two-thirds appear first, and its upper third at a later period, and quite
independently.

5. In very rare cases these two pieces do not unite, and then a
superficial gyrus connects the ascending frontal and ascending parietal
convolutions.

6. As a general rule, in the adult brain, some trace of the double origin
of the fissure of Rolando persists. At the point of union there is usually a
shallowing of the fissure, with either an interlocking of the boundary banks,
or, perhaps, a distinct deep annectant gyrus.

7. The fissure of Rolando, in its development, therefore corresponds
with the other two radial " Primarfurchen." They are all (i. e. prsecentral,
the fissure of Rolando, and the postcentral) developed in two pieces.

8. The inferior genu of the fissure of Rolando usually makes its appearance
before the superior genu.

9. After the fissure of Rolando is fairly laid down, the posterior bound-
ing-bank (i. e. the ascending parietal convolution) shows a greater growth
energy than the anterior bounding-bank (%. e. the ascending frontal
convolution).

10. The stability of position of the fissure of Rolando on the surface of
the cerebrum, at all periods of growth, is remarkable. In the adult the
upper fronto-Rolandic index is 53*3, and the lower 43*3. The only period
of development at which there is a marked deviation from this is between
the sixth and the eight months of intrauterine life, when the upper end of
the fissure is placed further back.