t
are perhaps the following.

Besides the regions instanced above, in the limbic (olfactory),
occipital (visual), and temporal (auditory) lobes, as exhibiting
precocity of development, there is a region showing similar precocity in
the fronto-parietal portion of the hemisphere. This is the region which
in the Primates includes the large _central fissure_ (sometimes called
the fissure of Rolando). To it fibres are traced which seem to continue
a path of conduction that began with afferent tracts belonging to the
spinal cord, and tracts which there is reason to think conduct impulses
from the receptor-organs of skin and muscles. The part of the cortex
immediately behind the _central fissure_ seems to be the main cortical
goal for these upward-conducting paths. That _post-central_ strip of
cortex would in this view bear to these paths a relation similar to that
which the occipital and temporal regions bear to afferent tracts from
the retina and the cochlea. There are observations which associate
impaired tactual sense and impaired perception of posture and movement
of a limb with injury of the _central region_ of the cortex. But there
are a number also which show that the motor defect which is a
well-ascertained result of injury of the _pre-central_ gyrus is
sometimes unaccompanied by any obvious defect either of touch or of
muscular sense. It seems then that the motor centres of this region are
closely connected with the centres for cutaneous and muscular sense, yet
are not so closely interwoven with them that mechanical damage inflicted
on the one of necessity heavily damages the other as well. There is
evidence that the sensory cortex in this region lies posterior to that
which has been conveniently termed the "motor." These latter in the
monkey and the man-like apes and man lie in front of the central
fissure: the sensory lie probably behind it. A.W. Campbell has found
changes in the cortex of the post-central convolution ensuing in the
essentially sensory disease, _tabes dorsalis_, a disease in which
degeneration of sensory nerve-fibres of the muscular sense and of the
skin senses is prominent. He considers that in man and the man-like apes
the part of the post-central gyrus which lies next to and enters into
the _central fissure_ is concerned with simpler sensual recognitions,
while the adjoining part of that convolution farther back is a "psychic
region" concerned with more complex psychosis connected with the sense