LIGHT AND LIFE. 117 



laborer, to fatten his cattle, shuts them up in stables lighted 

 by small, low windows. In the half-light 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 

 protean s. 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, 



