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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    a disposition which augments the field of vision, but exposes the eye to injury on this side. The cavity of the orbit contains, in addition, small masses of fat, which occupy the interspaces left between the organs of vision. This fat serves as a soft cushion for the globe of the eye to rest upon, and enables it to bear severe shocks without injury. Its absorption is very rapid in debilitated patients, and in those who suffer from cholera, which is the cause of the brown tint of the lids, and that sinking in of the eyes which gives their peculiar facial aspect to such patients. SECTION II. FUNCTIONS OP THE ORGANS OP VISION. Of the Exciting Agent of Luminous Impressions. Although the study of the laws of light belongs rather to physics than to physiology, it is indispensable, before describing the mechanism of vision, to state some of the chief points in optics. Of Light.—Light is an imponderable agent, which renders objects visible. Two hypotheses explain the mode of its trans- mission. The oldest, termed the emission theory, suggested by Newton, has been rejected by the greater number of physicists ] the ether, named the undulatory theory, proposed by Huyghens, and supported by Descartes, holds undisputed sway at present in science. This hypothesis supposes that light emanates from luminous bodies, and that it reaches us by a series of undulations resemblii^ those by which sound is propagated. The transmission of light takes place in straight lines, and it is propagated with inconceivable rapidity. The astronomer Roemer demonstrated by observations made upon the satellites of Jupiter that light occupies about eight minutes in traversing the distance which intervenes between the earth and the sun ] it must, therefore, travel at the rate of about 200,000 miles a second. It appears, nevertheless, that three years would elapse before the light emanating from the nearest fixed star would act on our retina, and thus, if such a star were obliterated from the heavens, it would still remain visible for the same space of time. It is not, therefore, astonishing that there are stars that have never