The organs of vision : their structure and functions / by G.J. Witkowski ; tr. by Henry Power.

  • Gustave-Joseph Witkowski
Date:
[1878?]
Catalogue details

Licence: Public Domain Mark

Credit: The organs of vision : their structure and functions / by G.J. Witkowski ; tr. by Henry Power. 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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    ders named rods, disposed like the several elements in a mosaic. One extremity of each is in contact with the choroid, and the other with the hyaloid membrane. The general aspect of the extremities, the sectional area of each of which is about 3-lOOOths of a millimetre, resembles a mosaic with microscopic tesserae. Some of the rods present a dilated extremity like a club, and are then termed cones. At the yellow spot cones alone are present. These microscopic bodies, the rods and cones, may be compared in their functions to the nervous papillae of the organ of touch. The central artery of the retina presides over the nutri- tion of the several layers of this membrane, and breaks up into an infinite number of capillaries in front of the layer of rods and cones, which explains the fact that under certain conditions they may be perceived. 6. Zonule of Zinn.—This fibrous membrane has the same form and general direction as the iris. The festoons of its peri- phery (152) give attachment to the retina, whilst the radii of its inner margin (151) surround the lens like a collar. This fibrous zone constitutes an organ of support which, on the one hand, stretches as far as the retina, and on the other maintains the lens in its vertical position, from which circumstance it has been termed the sus]oensory ligament. Its anterior surface presents a series of elevations and intermediate depressions, which interdigitate with the dliany processes (153). If a small opening be made through the zonule of Zinn, an entrance is made into an annular and prismatic canal, bounded in front by this zone, behind by the hyaloid membrane, and internally by the border of the lens. If a little air be blown into this canal through the artificial opening, elevations are produced, according to Petit, resembling those in silver ornaments, to which the term ‘ godronnd ’ has been applied. Hence the term of ‘ canal godronne,’ or frilled canal of Petit (151). (B.) Media of the Eye. 1. Aqueous Humour.—This limpid and transparent fluid occupies the space between the cornea in front and the lens be- hind, a space that is divided into two chambers by the iris—an anterior and a igosterior. The quantity of aqueous humour is very small, being estimated at only eight drops; it can, however, if evacuated, be reproduced with great rapidity. The aqueous humour loses its transparency and becomes turbid in various diseases of the eye; it may also contain fibrinous flocculi, and blood or pus. Foreign bodies which have perforated the cornea are sometimes found in the anterior chamber, as are also tumours, or condylo- mata implanted on the iris, a dislocated lens, or cysticerci. The