Inquiries respecting the anatomy of the eye / [Arthur Jacob].

  • Arthur Jacob
Date:
1823
Catalogue details

Licence: Public Domain Mark

Credit: Inquiries respecting the anatomy of the eye / [Arthur Jacob]. Source: Wellcome Collection.

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    respecting it will prove correct upon examination. In reptiles and fishes the nerve is not enclosed in a cellular or tubular cylinder as in mammalia, but folded in a peculiar manner, consequently in them, in place of a button or tuft presenting itself in the bottom of the eye, a stellated or crucial medullary projection has been observed, and may be well seen in the eye of the turtle, conger eel, and others: I have not myself, however, observed this appear¬ ance in those animals immediately after death. The facts just stated, if correct, are worthy of the particular attention of anatomists, as affording an excellent example of the extraordinary and im¬ portant changes which animal structure undergoes when the influence of vitality no longer predomi¬ nates over the operation of physical forces or che¬ mical affinities. What I have just said respecting the expression of the medullary part of the nerve in the form of vermicular coils, strengthens the opinion that the nerve consists of a number of tubes containing this medullary matter; but a care¬ ful examination of a longitudinal section leads rather to the conclusion that it is deposited in a cellular structure, or at least that the communica¬ tions between the medullary fibres are so frequent as to cause the part to assume such an appearance. Having removed the medullary part from a portion of the optic nerve of a whale by gentle pressure, and passing water through it, I filled it with mer¬ cury, and allowed it to dry ; upon making a longi¬ tudinal section of it, the surface presents an irre-
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