304 THE POPULAR SCIENCE MONTHLY. . . 



mulate in the organs. In the same way, for the sake of developing 

 enormous fat livers in geese, they are put into dark cellars, kept en- 

 tirely 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 cellars. In certain underground lakes of Lower Carniola we find 

 very singular reptiles resembling salamanders, called proteans. They 

 are nearly white, and have only the rudiments 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 de- 

 stroyed the color of their skins and their visual organs. 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 mushroom, unconscious of the healthy contact of lumin- 

 ous radiance. 



William Edwards, to whom science owes so many researches into 

 the action of natural agents, studied, about 1820, the influence exer- 

 cised 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 pa- 

 per. 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, others shielded from the 

 light. The tadpoles that were shone upon, soon underwent the change 

 into the adult form, while the others either continued in the tadpole 

 condition, or passed into the state of perfect frogs with great diffi- 

 culty. Thirty years later, Moleschott performed some hundreds of 

 experiments in examining how light modifies the quantity of carbonic 

 acid thrown off in respiration. Operating on frogs, he found that the 

 volume of gas exhaled by daylight exceeds by one-fourth the volume 

 thrown off in darkness. He established, in a general way, that the 

 production of carbonic acid increases in proportion to the intensity of 

 light. Tims, with an intensity represented by 3.27, he obtained 1 of 

 carbonic acid, and, with an intensity of 7.38, he obtained 1.18. The 

 same physiologist thinks that in batrachians the intensity of light is 

 communicated partly by the skin, partly by the eyes. 



Jules Beclard made more thorough researches. Common flies'- 

 eggs, taken from the same group, and placed at the same time under 

 differently-colored glasses, all produce worms. But if the worms, 

 hatched under the different glasses, are compared at the end of four or 

 five days, perceptible differences may be seen among them. Those 

 most developed correspond with the violet and blue ray ; those hatched 

 under the green ray are far less advanced; while the red, yellow, and 



