Bauhaus-Universität Weimar

Titel:
Dictionary of philosophy and psychology including many of the principal conceptions of ethics, logics, aesthetics ... and giving a terminology in English, French, German and Italian, vol. 1 [a-laws]
Person:
Baldwin, James Mark
PURL:
https://digitalesammlungen.uni-weimar.de/viewer/image/lit29445/159/
BRA TN 
Although the arrangement and distribution 
of cortical elements varies in different regions, 
they may he conveniently included in four 
layers outside of the white matter. The most 
superficial zone is sparsely provided with cells 
in which ramify the dendrites of the deeper 
nerve cells. In this layer also originate the 
tangential fibres connecting with other re¬ 
gions. This is the tangential fibre zone (also 
molecular, neuroglia, or Cajal-cell layer). The 
second layer is filled with small pyramidal 
cells, which tend to increase in size in deeper 
portions, forming a transition to the third 
layer of large pyramids. Beneath the latter is 
a zone of variously placed polymorphic cells. 
The relations between the cells of these 
layers are seen in Plate B (Brain), Fig. 2. 
to the lower centres, collecting in the corona 
radiata, and afterwards constituting the in¬ 
ternal capsule, are there segregated somewhat 
in accordance with their sources ; and, accord¬ 
ingly, various parts of the capsule contain 
fibres with different functions. See Localiza¬ 
tion. 
The speech centre (Broca’s region) contri¬ 
butes a special tract to the pyramids. The 
parietal motor zones are also represented by 
more or less distinct bands in the internal 
capsule. The optic radiations connect the 
optic centres of the thalamus with the occipital 
cortex, and it is probable that each sensory 
area has its reflex tract connecting with the 
appropriate lower centres. Special tracts from 
the striatum pass to the tegmental nuclei. 
Gyr. fusiformis 
Fig. 6. Median longitudinal section through the human brain. After Edinger. 
The pyramidal cells give rise to strong neurites, 
which extend into projection-tract fibres and 
which occasionally give off strong collaterals, 
passing via the callosum to homologous regions 
of the opposite hemisphere. Other cells send 
their neurites into the tangential zone out¬ 
ward : see Association Fibres. 
The framework of the cortex is originally 
supplied by the spongioblasts of the endyma 
(see Nervous System, Histogenesis), and, in 
the adults of the lower animals, these cells 
continue to span the entire thickness of the 
cortex. In the massive cerebrum of higher 
animals the so-called neuroglia cells supple¬ 
ment the primitive spongioblastic framework. 
The neurites of the cortical cells destined 
Cerebellum. Although derived from out¬ 
growths of the lateral walls of the metacoele, 
the cerebellum in mammals consists of a me¬ 
dian vermis and two lateral hemispheres, with 
two or more smaller paired bodies (flocculi). 
The surface is marked by convolutions and 
depressions analogous to the gyri and fissures 
of the cerebrum. The cortex of the cerebellum 
(Fig. 8) is extraordinarily complex, and beauti¬ 
fully illustrates the apparatus for nervous 
discharge by contiguity rather than by struc¬ 
ture continuity. Three layers may be dis¬ 
tinguished above the white fibre zone. Of 
these the middle layer, composed of the cells 
of Purkinje, is most important. These large 
pyramidal cells are in a single layer, and their 
k 2 
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