Freiburger historische Bestände - digital

126

Cunningham Memoirs.

obtained from the measurement of sixty-four brains (thirty-two male, thirty-
two female). More recently, however, he has given us the results of a very
much more extended inquiry in which he has measured nearly four hundred
hemispheres.* He has come to the conclusion that the Sylvian fissure
is, on an average, longer in the left hemisphere than in the right, and,
further, that it is longer in the male than in the female. It will be necessary
to study his data somewhat in detail. He states that the posterior
horizontal limb of the Sylvian fissure "in one hundred and seventy left
hemispheres presented an average length of 58"2 mm.; in one hundred
and eighty-three right hemispheres an average length of 51*8 mm. The
difference in favour of the left side is therefore, on an average, 6*5 mm.
Still these results will be more apparent if I add that in one hundred
hemispheres the following lengths occurred:—

Under and up to 50 mm., . . . Left, 22 times ; right, 45 times.

Prom 51 to 60 mm., 42 ,, ,, 44 ,,

From 61 to 70 mm., . . ,, 27 ,, ,, 11 ,,

Over 70 mm., . . . ,, 9 ,, ,, 0-6 ,,

Whilst, therefore, the great majority (nine-tenths) on the right side
presented a length under 60 mm., a full third on the left side overstepped
this length."

In this investigation, Eberstaller only deals with the absolute length of
the fissure as he observed it in the two hemispheres, and, although the
results which he lays before us are very striking, it would have been more
satisfactory had he given us the means of studying the relative length of
the fissure on the two sides. It is generally understood that the left hemisphere
presents an average length which is slightly greater than that of the
right hemisphere, and it would be reasonable to suppose that the absolute
length of the Sylvian fissure on the left side would, in correspondence with
this, be greater than that of the right side. It is true, the great average
difference between the two fissures of 6-5 mm. could hardly be accounted
for in this manner, but this does not lessen the necessity of our obtaining
relative as well as absolute results.

* Das Stirnhirn. Wien und Leipzig, 1890.