A microscopic description of the eyes of the Monoculus polyphemus Linnaei / by William André ; communicated by Sir Joseph Banks.

  • André, William, 1743-1807.
Date:
1782
Catalogue details

Licence: Public Domain Mark

Credit: A microscopic description of the eyes of the Monoculus polyphemus Linnaei / by William André ; communicated by Sir Joseph Banks. 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.

    3/8 (page 5)
    mufl be removed from the fhell, and applied to a fingle mi- crofcope with a very ftrong light. The internal furface of the large eyes, examined with the microfcope, is found to be thick fet witn a great number of fmall, tranfparent cones, of an amber colour *, the bafes of which Hand downward, and their points upwards next the eye of the obferver +. The cones in general have an oblique direc- tion, except fome in the middle of the cornea, about thirty in number, the direction of which is perpendicular. The center of every cone being the moft tranfparent part, and that through which the light paffes ; on that account the perpendicular or central cones always appear beautifully illuminated at their points. In a word, they are all fo difpofed as that a certain number of them receive the light from whatever point it may iflue, and tranfmit it to the immediate organ of fight, which we may reafonably fuppofe is placed underneath them; but this lafi: circumftance can only be determined in a recent fub- je<St, which I have never been fo lucky as to fee. The cones are not all of the fame length ; thofe on the edges of the cornea are the longefi:, from whence they gradually diminifh as they approach the center, where they are not above half the length of thofe on the edges, fee fig. 2. As thefe cones fo e^fily tranfmit the light through their fubftance, when I firfi: examined them I thought they were tubes; but I have fince viewed them broken in different direc- tions, and am convinced they are folid tranfparent bodies. If they be viewed with a deep magnifier, every cone appears di- vided tranfverfely by two or three internal fepta or partitions. * 1 have made fome attempts to afcertain their number, and think they amount to about 1000. f This Eiuii be reverfed if the eye be conlidered in its natural pofition. This