ences acting at once, and light does not play the sole part in them. Heat and other conditions of the medium probably have a share in these operations of color. Still, the peculiar and powerful effect of luminous radiation as a part of them is beyond dispute.
The whole system of organic functions shares in the benefits of light. Darkness seems to favor the preponderance of the lymphatic system, a susceptibility to catarrh in the mucous membranes, flaccidity of the soft parts, swellings and distortions of the bony system, etc. Miners and workmen employed in ill-lighted shops are exposed to all these causes of physiological suffering. We may notice, with regard to this, that certain rays of the solar beam affect animals like darkness; among others, the orange light, which, according to Bert, hurts the development of batrachians. Now, if this light is injurious to animals, it is not so to plants, as we have seen. In exchange, green light, which is hurtful to vegetables, is extremely favorable to animals. There is a kind of opposition and balance, then, as respects luminous affinities, between the two great kingdoms of life. White light, as Dubrianfant says, seems to split up under the influence of living beings into two complementary groups, a green group and an orange group, which exhibit in Nature antagonistic properties. It is quite certain that green light is a very lively and healthful stimulant for our functions, and that, for that reason, spring is the favored and enchanted season.
The correspondence between perfection of forms and heightening of luminous intensity proves true in the human race as in others. Æsthetics, agreeing with ethnography, demonstrate that light tends to develop the different parts of the body in true and harmonious proportion. Humboldt, that nice observer, says, speaking of the Chaymas: "The men and women have very muscular bodies, but plump, with rounded forms. It is needless to add that I have never seen a single one with any natural deformity. I will say the same of so many thousands of Caribs, Muycas, Mexican and Peruvian Indians, whom we have observed during five years. These bodily deformities and mis-growths are extremely rare in certain races of men, especially among people who have a deep-colored skin." No doubt there is great difficulty in conceiving how light can model—can exert a plastic power. Yet, reflecting on its tonic effect on the outer tegument, and its general influence over the functions, we may assign it the part of distributing the vital movement orderly and harmoniously throughout the whole of the organs. Men who live naked are in a perpetual bath of light. None of the parts of their bodies are withdrawn from the vivifying action of solar radiation. Thence follows an equilibrium which secures regularity in function and development.
It is commonly said that an ordained causality rules the operations of matter, and that free spontaneity is the privilege of those of spirit. It might well be said on this subject that, in many cases, the causes