Turning to the animal kingdom, which is more immediately our province, we find in that portion of nature an equal dependence on light for its proper development and vitality. Animals droop when they are deprived of light; there are instances on record where persons having been long confined in dark places or dungeons (even though well ventilated), their whole complexion has become sallow, their general health deteriorated, pustules, with aqueous humours, have opened out upon their skin, and they have become languid, and frequently dropsical. In the absence of light, there is a predominance of the white fluids of the body; the action of the lymphatic system is exalted, and it imparts to the organization of animals that remarkable blanched appearance called ‘etiolement.’ Hence the well-founded supposition, that the absence of the solar rays of light contributes greatly to the development of scrofula. “Let in the sun, and you shut out the doctor,” says an old Italian proverb. The effects of the free admission of light, as a point of great importance to the well-being of every individual, has been proved by the experiments of Dr. Edwards, who has shown that if tadpoles be nourished with proper food, and exposed to the renewed action of water (so that their bronchial respiration may be maintained), but are entirely deprived of light, the growth continues, but their metamorphosis into the condition of air-breathing animals is arrested, and they remain in the form of large tadpoles. Dr. Edwards also observes, that persons who live in caves and cellars, or in very dark, narrow streets, are apt to produce deformed children. Rabbits, which were kept in a dark cellar, were affected with mollities ossium, their limbs being useless. It has been recently stated, that the cases of disease in the dark side of an extensive barrack at St. Petersburgh, have been uniformly, for many years, in the proportion of THREE to one to those on the side exposed to a strong light. Dupuytren relates the case of a lady whose maladies had baffled the skill of several eminent practitioners. This lady resided in one of the narrow streets of Paris, and in a dark room in which the sun never shone. After a careful examination, Dupuytren was led to refer her complaints to the absence of light, and recommended her removal to a more cheerful situation: the change was followed by the most beneficial results; all her complaints in a very short time vanished. In a series of experiments made by Mr. Simon upon cats, which that gentleman confined in dark cellars, he found after death disease of the kidney, resembling that morbid state of the gland generally known as morbus Brightii (Bright’s disease), and, in other cases, incipient fatty degeneration of the liver.