Observations on the canal of petit / by Thomas Spencer Cobbold.

  • Thomas Spencer Cobbold
Date:
MDCCCLII [1852]
Catalogue details

Licence: Public Domain Mark

Credit: Observations on the canal of petit / by Thomas Spencer Cobbold. Source: Wellcome Collection.

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

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    The recent descriptions of the membranula of Zinn, under the name of Liga- mentum suspensorium, by Professor Retzius of Stockholm, has added most im- portant details in explanation of this difficult structure; and it has been still further elucidated by the excellent observations and lectures of Mr Bowman. ^ If the external coverings be removed from the eye of a calf or lamb at full time, leaving the vitreous body and lens, with their membranes, entire; and if the membranula of Zinn, which is usually considered as the anterior wall of the canal of Petit, be examined with a power of thirty diameters, a number of minute specks, having the appearance of foramina, are brought into view. These specks Jacobson supposed to be apertures of communication between the canal of Petit, and the posterior chamber, allowing the aqueous humour to pass freely from the one to the other. ^ K these specks are more minutely examined, they will be found to be nuclei situated below the membranula of Zinn; and in a rolled or folded portion of the hyaloid, which constitutes essentially the canal of Petit; and exhibits, like the hyaloid in the rest of its extent, a nucleated structure. If the membranula of Zinn be now removed, a distinct view will be obtained of these nuclei imbedded in a membrane, which is arranged in a ring-shaped, festooned, and hollow fringe, extending all round the margin of the capsule of the lens, and in the situation of the canal of Petit. I have represented this fringe in fig. 1, as it appears after raising the membranula of Zinn, which, when completely removed, allows the outer margin of the fringe to curl forwards and inwards, exhibiting in its surface numerous radiating folds, and a festooned ar- rangement at its free margin. Each of these folds and festoons is somewhat distended by the fluid contained within the ring-shaped cavity of the fi-inge; and is separated from the others by crevices which, as well as the festoons and folds, do not appear to be permanent, but due to the gathering or puckering together of the entire fringe round the margin of the capsule of the lens. The crevices present the appearance of curved lines, sweeping from the margin of the lens Fig. 1. upon its under surlace. ' Bowman.-Lectures on the parts concerned in the operations on the Eye. Lon- don, 1849. 2 Jacobson. Suppl. ad Oplhalmiatr. Copenhag,,