A textbook of mental diseases.

  • Lewis, W. Bevan.
Date:
1899
Catalogue details

Licence: Public Domain Mark

Credit: A textbook of mental diseases. Source: Wellcome Collection.

Provider: This material has been provided by UCL Library Services. The original may be consulted at UCL (University College London)

    176/749 (page 124)
    the hemisphere. It is these more complex forms of cortex -which concern us chiefly ; they comprise in man the extensive areas at the vertex and the whole convoluted surface of the hemispheres, as seen from above. Now, in studying the small brain of the rodent and higher animals, we find structural modifications in the cortex of this region, which appear to foreshadow the divergences observed in man. Thus, if we examine successively the cortex at different points from within outwards in a vertical section through the hemisphere, passing through the Sylvian depression, we find that— (a) The first layer of the cortex is deepest at the sagittal border, and steadily diminishes in depth as we proceed outwards towards the limbic fissure; (6) The second layer of small pyramidal cells increases rapidly in depth and in wealth of cell-structure in a reverse direction—i.e., from within outwards; (c) The ganglionic series of cells (which assume thick clustered nests in the upper limbic arc and over the vertex bordering on the sagittal fissure), gradually loses its confluent tendency and becomes spread out in isolated units ( solitary type) as we approach the limbic fissure externally. On the other hand, if we examine similarly a vertical section taken through the posterior moiety of the upper limbic arc (Plate vi.) we find that— {d) The intercalated series of granule cells increases in richness of elements and depth of formation as we proceed outwards to the lateral aspects of the hemispheres, and backwards to the occipital pole ; and reaching the limbic fissure terminates abruptly, whilst the other layers pass on uninterruptedly. If we now examine vertical sections of the hemisphere in the antero-posterior plane, we find that— (e) The outer layer (peripheral zone) progressively diminishes in depth from the frontal to the occipital pole; (/) The small pyramidal cells of the second layer diminish in size in the same direction ; (g) The granule or angular cells intercalated in the five-laminated cortex increase in richness conspicuously towards the occipital pole; (h) Lastly, the ganglionic series, which near the frontal pole forms a deep layer rich in cell elements, thins out considerably backwards into a laminar or solitary formation; but, at the extreme occipital pole, these cells again form a somewhat deep belt with granule cells superimposed. The obvious deductions to be made from the foregoing are that <5ertain elements preponderate in certain fixed areas of the cortex, and that the development of certain layers appears to exclude that of another series. Thus the frontal pole and frontal extremity of the upper limbic arc are especially characterised by the preponderance of