Relations of diseases of the eye to general diseases : forming a supplementary volume to every manual and text-book of practical medicine and ophthalmology / Ed. by Henry D. Noyes.

  • Knies, Max.
Date:
1895
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Licence: Public Domain Mark

Credit: Relations of diseases of the eye to general diseases : forming a supplementary volume to every manual and text-book of practical medicine and ophthalmology / Ed. by Henry D. Noyes. Source: Wellcome Collection.

Provider: This material has been provided by the Harvey Cushing/John Hay Whitney Medical Library at Yale University, through the Medical Heritage Library. The original may be consulted at the Harvey Cushing/John Hay Whitney Medical Library at Yale University.

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    According to theoretical considerations, partial destruction of one perceptive centre would give rise to a strictly homonymous loss of the field of vision (negative scotoma) of a corresponding size in the vicinity of the point of fixation of each eye. Wilbrand ( Die hemi- anopischen Gesichtsfeldformen, Wiesbaden, 1S90, p. 5) is also in- clined to assume a circumscribed hemorrhage into the perceptive centre of one side in a case of this kind under clinical observation. It might also be due to a small hemorrhage at the entrance of the tractus into the primary optic ganglia, perhaps even into the latter. Post-mortem examinations alone can decide such points. Hun's case (Amer. Journ. of Med. Sc, Jan., 1887) is the only one known to me. After an attack of apoplexy a man lost the left lower quadrants of the fields of vision and the peripheral parts of the left upper quad- rants. A lesion was found in the lower (?) half of the right cuneus. [For similar cases see Henschen.] Experiments on animals (the last ones by Obregia, Schaefer, Munk, etc.), with which clinical experience in man agrees, reveal another function of the occipital cortex. By stimulating the occipital cortex of one side with feeble currents conjugate movements of both e3Tes toward the opposite side are produced, in a somewhat upward direc- tion when the posterior part is irritated, in a downward direction when the anterior part is irritated. Hence the occipital cortex also exercises motor activity and, as we shall see later, brings about vol- untary movements of adjustment of both eyes upon an object which is appearing in the opposite half of the field of vision. Further de- tails will be furnished under the heading of the central disorders of the ocular muscles. Experiments on animals can be utilized for man only after the exercise of caution. The most reliable are those on monkeys, although even they present considerable anatomical differences from man. The different condition in many animals as regards decussation in the chiasm in itself enjoins caution, and still more the fact, for example, that birds are probably able to see after removal of the cerebral cortex, while the mammalia are not. In such cases parallels cannot be established even between larger parts of the brain which apparently are per- fectly homologous. Among clinical observations cases of softening are the most valuable, be- cause they are most sharply defined ; hemorrhages are less valuable, tumors leasl of all. Every rapidly or suddenly developing lesion gives rise, apart from the sj mptoms which correspond to its situation, to other more or less remote symp-
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