Freiburger historische Bestände - digital

56

Cunningham Memoirs.

These indices are very instructive. They show that it is not until
after birth that the occipital lobe attains its full development. During
intra-uterine life it is shorter than it is at later stages in the growth of
the brain. Broadly speaking from the fifth to the eighth month of
festal life the occipital index may be said to be 18 -8. From the eighth
month to the full term of intra-uterine life the occipital lobe grows
relatively at a rapid rate, and the occipital index of 20-8 is attained. The
next stages in the growth-history of this lobe are peculiar, because it
would appear that during the first five years of extra-uterine life it attains
its maximum relative length, and presents finally an index of 23*2. It
does not maintain this length, however, because as growth goes on, the
occipital lobe becomes relatively shorter, until we obtain for the adult
the index of 2T2.

Eberstaller* states that in 200 hemispheres he has measured the mesial
border of the mantle, and calculated the relative position upon this of
the parietooccipital fissure. The relative distance of the fissure from
the occipital pole with reference to the length of the cerebral border he
reckons to be as 1 : 6. These figures, however, cannot be compared with
mine, because Eberstaller measures the border of the hemisphere from
the locus perforatum anticus in front to the occipital pole behind. My
" mesial cerebral length " is obtained by measuring from the anterior end
of the cerebrum in front to the occipital pole point behind.

In right and left hemispheres the occipital index is apparently the
same. In forty-five right adult hemispheres the index was 21*2; in
thirty-seven left adult hemispheres it was 21*3.

But there appears to be a sexual difference in this respect. In the
female the occipital lobe is relatively longer than in the male. Forty,
seven adult male hemispheres afforded an occipital index of 20-8 ; whilst
35 adult female hemispheres gave an average index of 21*7.

The parietal indices, expressing as they do the relative mesial length of
the parietal lobe, also yield us some interesting information. We note
that in the early foetus (5J to 6| months), this lobe is relatively long,

* Zur Oberflachen-Anatoniie der Grosshirn-Hemispbaren. (Yorlaufige Mittheilung.) No. m.
Wiener Medizinische Blatter, No. 19, 1884, p. 580.