Freiburger historische Bestände - digital

324

Cunningham Memoirs.

(a) Relative Measurements.—The far higher value of relative measurements
is sufficient reason for not dealing with the question of the topography
of the ends of the fissure chronologically.

Thane stated that if the total distance from the fronto-nasal suture, i. e.
the nasion to the inion or occipital protruberance, were taken and divided
equally in two, that a spot J inch behind the halfway point in the nasio-
inial line would mark the upper end of the fissure.

Hare, by examining a series of 10 heads with the cerebrum in situ, came
to the conclusion that in front of the upper end of the fissure we should find
•55 of the total length from the glabella to the inion.

Prof. Cunningham has shown that the position of the upper end of the
fissure of Rolando is very constant in relation to the rest of the hemisphere.
Further, that in comparing the position of the upper end to the bregmatic
portion of the coronal suture the distance lengthens during the passage
from the sixth month of intra-uterine life to the adult state two-fold. This
difference* of 2 to 1 is, however, lost to a large extent by birth, and the
difference then is as 18 to 16, the length of the hemisphere being 100. In
employing these facts for localization it would be necessary to allow for
the thickness of the skull and coverings in taking the length of the hemisphere
which is to form the basis of the calculation ; but whatever mode of
finding the upper end of the fissure be employed, these indices will sufficiently
correct the position according as that is altered by age. Another
important practical point discovered by Prof. Cunningham is that there is
.a sexual difference in this question, the average corono-Rolandic indices
upper and lower, and in the male and female, respectively, being 16 and
12*1 for the former, and 17*5 and 13-9 for the latter.

The same fact is also shown to be true by Altoukhoff.

Muller by an ingenious and original method determined the position
of the chief sulci as follows:—Measuring from the glabella to the inion he
took a mesial arc, i.e. the usual antero-posterior distance, and in addition
a horizontal arc between the same points. By then simply dividing these
two arcs into one hundred equal parts, and joining them at intervals of

* In confirmation, consult the evidence obtained from the lower apes.