LIGHT AND LIFE. 117 
laborer, to fatten his cattle, shuts them up in stables lighted 
by small, low windows. In the halflight of these prisons 
the work of disassimilation goes on slowly, and the nutri- 
tive substances, instead of being consumed in the circulat- 
ing fluid, more readily accumulate in the organs. In the 
same way, for the sake of developing enormous fat livers _ 
in geese, they are put into dark cellars, kept entirely quiet, 
and crammed with meal. 
Animals waste away as plants do. The absence of 
light sometimes makes them lose vigor, sometimes entirely 
changes them, and modifies their organization in the way 
least favorable to the full exercise of their vital powers. 
Those that live in caverns are like plants growing in cel- 
lars. In certain underground lakes of Lower Carniola we 
find very singular reptiles resembling salamanders, called 
proteans. They are nearly white, and have only the rudi- 
ments of eyes. If exposed to light they seem to suffer, 
and their skin takes a color. It is very likely that these 
beings have not always lived in the darkness to which they 
are now confined, and that the prolonged absence of light 
has destroyed the color of their skins and their visual or- 
gans. Beings thus deprived of day are exposed to all the 
weaknesses and ill effects of chlorosis and impoverishment 
of the blood. They grow puffy, like the colorless mush- 
room, unconscious of the healthy contact of luminous radi- 
ance. 
William Edwards, to whom science owes so many re- 
searches into the action of natural agents, studied, about 
1820, the influence exercised by light on the development 
of animals. He placed frogs’-eggs in two vessels filled 
with water, one of which was transparent, and the other 
made impermeable to light by a covering of black paper. 
The eggs exposed to light developed regularly; those in 
the dark vessel yielded nothing but rudiments of embryos. 
Then he put tadpoles in large vessels, some transparent, 
