Lectures of the diagnosis of diseases of the brain / by W. R. Gowers.

  • Gowers, W. R. (William Richard), 1845-1915.
Date:
1885
Catalogue details

Licence: Public Domain Mark

Credit: Lectures of the diagnosis of diseases of the brain / by W. R. Gowers. Source: Wellcome Collection.

Provider: This material has been provided by The University of Leeds Library. The original may be consulted at The University of Leeds Library.

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    VISUAL 1>A'1'H. ■blind. The balance of evidence at present collected seems to show that this difference does not depend on the seat of the disease causing the heniiopia ; and it can therefore only be explained by iiidi\ddual differences in the decussation. In many indi\'iduals, it would seem, fibres from a small area around the centre of the macula pass by each optic tract; while in some persons, each tract contains fibres from only one half of the macular region, as it does from the rest of the retina. Another form of variation seems to show also that there are considerable differences in the character of the decussation. Above and below the fixing point, the line of division is also often irregular, sometimes, for instance, sloping Fig. 9.—Right Hemiopia from Cerebral Disease, showing an irregu- lar OBLIQUE LINE OF DIVISION, PROBABLY DUE TO AN UNUSUAL FORM OF DECUSSATION. off to one side above, and to the other side below, the two fields corresponding closely. In an extreme example of this, such as is shown in Fig. 9, the division becomes irregularly oblique instead of vertical. It is impossible to explain this, except on the theory of variations in the decussation. Some facts suggest that there are similar variations in some other decus- sations in the nervous system, especially in that of the sensory tract from the skin. The visual path passes in the optic tract, by the corpora geniculata, through the white substance of the hemispheres, to the cortex of the occipital lobe on the outer surface. If it is destroyed anywhere in this course, the result is hemiopia of the same character. Disease of the cortex of the occipital lobe has a like effect. There is no complementary decussation at the corpora quadrigemina, as has been fancied. VVliether