On the meaning of the words 'nyctalopia' and 'hemeralopia' : as disclosed by an examination of the diseases described under these terms by the ancient and modern medical authors / by John Tweedy.

  • Tweedy, John, 1849-1924.
Date:
1882
Catalogue details

Licence: Public Domain Mark

Credit: On the meaning of the words 'nyctalopia' and 'hemeralopia' : as disclosed by an examination of the diseases described under these terms by the ancient and modern medical authors / by John Tweedy. 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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    includes men old enough to engage in battle, and to many.^ The disease may, therefore, be said to occur not only in children (TratSe?), but also in young adults up to the age of forty. Moreover, the statement, presently to be discussed, that married women are not subject to the complaint, also implies that the disease is not exclusively one of childhood. Colour of the eyes, etc.—Dark eyes and eyes with small pupils are said to be especially predisposed to Hippocratic nyctalopia.^ Aristotle and other authors state these eyes show a similar predisposition to night-hlindness. In treating of some of the causes of the difference in colour of the eyes of different individuals, Aristotle remarks that it had been assumed, on insufficient grounds, that pale blue eyes ('ykavKo/xjjLaTa) have more of fire, as Empedocles had said, and dark eyes (geXavogfiara) more of water than of fire; adding that it had been incorrectly stated that lack of moisture is the reason why blue eyes cannot see well by day, as want of fire is the reason why black eyes cannot see well by night.^ In opposition to this view Aristotle asserts, with Democritus, that in every case vision is of water, and not of fire.* The eye is made of water, because this is trans- parent ; and the amount of fluid (to vypov) in the eye determines the colour of the eye. Eyes that have much moisture are dark, and those that have little are blue. This is the reason why blue eyes cannot see well by day, or black eyes by night; because blue eyes, on account of the scarcity of their moisture, are too much agitated by the light, whereas black eyes, from an excess of moisture, are not so easily set in motion.® Moreover, nocturnal hght is very feeble, and does ' Herodt. iv, 72, 112, 114 and 115. * “Epid.,” vi, sec. vii, 1. ^ “Do Generat. Animal.,” lib. v, c. i. Iht'd.; and ‘‘ De Sensu,” c. ii. ® Aristotle’s theory of vision was that visible objects sot in motion a transparent medium between them and the eye, and that this motion is, in its turn, communicated to the sense-organ. “ De Anima.,” lib. ii, c. vii; De Sensu,” c. ii and iii; “ De Gcncrat. Animal.,” lib. v, c. i.