On single and correct vision : by means of double and inverted images on the retinae / by W.P. Alison.

  • William Pulteney Alison
Date:
1836
Catalogue details

Licence: Public Domain Mark

Credit: On single and correct vision : by means of double and inverted images on the retinae / by W.P. Alison. Source: Wellcome Collection.

Provider: This material has been provided by The Royal College of Surgeons of England. The original may be consulted at The Royal College of Surgeons of England.

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    of Newton is still defective. Several additions to our knowledge on the subject have been made since the time of Reid. 1. The supposition of the semi-decussation of the optic nerves, and con- sequent connexion of half of the retina of each eye with one of the optic lobes in the human body, has acquired additional pro- bability from the observation, first apphed to the subject by Dr Wollaston, of that form of temporary loss of vision formerly called Sujfusio dimidians, in which, although both eyes are open, one-half of the field of vision disappears from the sight; which is easily conceivable on the supposition of the right half of each retina being connected with the same portion of the sensorium, and not easily understood on any other supposition.* 2. That the commissure of the optic nerves is really a partial decussation in all animals where it exists, seems to me, if not absolutely ascer- tained, to be put on very strong ground, by the dissections of Mayo and the observations of Serres. Of the dissections of Mr Mayo, made after the nervous fibrils were hardened by alcohol, in the human body, we have a distinct record in his engraving of the commissure of the optic nerves (PI. vii. fig. 3. of his Engravings ; fig. 1. of the plate hereto an- nexed), of the accuracy of which I am satisfied, from some trials which I have myself made in the same manner, and in which it dis- tinctly appears, that the outer portion of each optic nerve is formed by fibres proceeding forward from the outer part of the tractus opticus of the same side, and that some fibres, at least, of the inner portion of each optic nerve, have crossed over from the inner part of the tractus of the opposite side, as sup- posed in this theory. The result of the inquiries of Serres on this point, in various animals, is stated as follows. He never could satisfy himself on the subject by preparations either of the human body, or others * This affection is sometimes quite transient; but in other cases, as I have my- self known, it is permanent, at least for weeks together.
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