Freiburger historische Bestände - digital

Dr. Cunningham— Surface Anatomy of the Primate Cerebrum. 155

In one male foetus (fig. 3) there was only one anterior limb. This was
crossed at its base by the coronal line, whilst the remainder of it was placed
in front of the suture. In the figure this fissure seems to possess the Y-shaped
arrangement, but this is not the case, as the upper of the two branches is
merely a secondary sulcus.

In all the other full-time foetuses examined, both of the anterior limbs
were placed completely in front of the coronal line.

In the adult head the variations in the position of the anterior limbs of
the Sylvian fissure with reference to the cranial wall are confined within
certain definite limits, and seem to depend upon : (1) the length of the
spheno-parietal suture ; (2) the extent of the overlapping squamous portion
of the lower part of the anterior border of the parietal bone; (3) the extent
of the overlapping portion of the squamous upper margin of the
great wing of the sphenoid ; (4) the degree of development of the pars
triangularis of the inferior frontal convolution ; and (5) the level at which
the Sylvian fissure is placed on the surface of the hemisphere. Putting
individual peculiarities aside we may state in general terms that in the
adult the anterior horizontal limb coincides with the upper border of the
great wing of the sphenoid bone, and that the ascending limb takes origin
at the postero-superior corner of the same bone, and extends upwards and
forwards behind the external coronal line, so that its extremity reaches or
perhaps may be crossed by the external suture.

In the youth of fifteen years old, and in the girl of eleven years old, the
conditions observed do not deviate very much from those that we have
indicated as being typical in the adult. In the boy of twelve years old,
however, the single anterior limb is relatively further in advance in relation
to the external coronal line. This is no doubt due in the first place to the
fact that only one limb is present, and in the second place to a slight degree
of development of the squamous bone overlapping part of the parietal bone.

In the children of four and five years the high position of the Sylvian
fissure on the surface of the cerebrum and the low squamous bone and great
wing of the sphenoid bring about a condition very different from that
present in the adult. The two anterior limbs are placed high above the
level of the spheno-parietal and spheno-frontal sutural line, and even come

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