LIGHT AND LIFE. 123 
this spontaneous movement of the infant’s eyes is thwarted, 
strabismus may be the consequence. 
Of all our organs the eye is the one that light especially 
affects. Through the eyes come all direct notions of the 
outer world, and all impressions of an esthetic kind. Now, 
the excitability of the retina shows variations of every 
kind. Prisoners confined in dark cells have been known to 
acquire the power of seeing distinctly in them, while their 
eyes also become sensitive to the slightest changes in the 
intensity of light. In 1766 Lavoisier, in studying certain 
questions upon the lighting of Paris, which had been given 
for competition by the Academy of Sciences, found, after 
several attempts, that his sight wanted the necessary sensi- 
tiveness for observing the relative intensities of the differ- 
ent flames he wished to compare. He had a room hung 
with black, and shut himself up in it for six weeks in utter 
darkness. At the end of that time his sensitiveness of 
sight was such that he could distinguish the faintest differ- 
ences. It is very dangerous, too, to pass suddenly from a 
dark place into a strong flood of light. The tyrant Diony- 
sius had a building made with bright, whitewashed walls, 
and would order wretches, after long seclusion from light, 
to be suddenly brought into it. The contrast struck them 
blind. Xenophon relates that many Greek soldiers lost 
their sight from reflections off the snow in crossing the 
mountains of Armenia. All travelers who have visited 
the polar regions have often seen like results produced by 
the glare of the snow. When'the impression of light on 
the eye is sudden and overpowering, the retina suffers 
most. If it is less powerful, but longer continued, the 
humors of the eye are affected. The phenomenon called 
sunstroke results from the action of light, and not, as is 
often supposed, from excessively high temperature. It 
sometimes occurs in the moderately warm season of spring; 
or a very intense artificial light, and particularly the elec- 
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