It is not our design to discuss here the dietetics or even the chemistry of food. There is, however, one branch of the subject that calls for a passing remark—the value of foods for special purposes. As the agriculturist is now carefully considering the adaptation of soils to the various kinds of vegetation, and is also inquiring into the character of those fertilizers that will continue and increase the growth-producing qualities of his land, so the physiologist is seeking to discover the special value of different aliments for all conditions of health and disease. The problem is necessarily somewhat difficult, but the end is so desirable—nothing less than human safety, comfort and development—that it is one of the most worthy of all the questions of science. Wholesome food, cheap food, and appropriate food for all classes and conditions is its aim. What does the weary brain require? What will give strength to muscle? How may the impoverished blood be enriched? How can vigorous, symmetrical growth be secured to childhood and youth? These are vital questions. Even when applied to the wants of the lower animals they are of immense importance. What conditions are most favorable for fattening cattle? What will give greatest strength and best sustain continuous exertion. Note a simple instance of one result of such inquiry. In ascertaining the food value of cottonseed, the revenue of our cotton crop is said to have been doubled. In medical practice physicians are more and more inclined to depend upon their knowledge of the principles of alimentation and the adjustment of proper nourishment to the sick than upon artificial stimulants or medicines. THE CIRCLE COMPLETED. We conclude this article on the chemistry of organisms, with the somewhat humbling reflection that to all living beings there comes a time when vitality yields to the power of those chemical forces, which resolve them again to their original inorganic forms. It can not be that this was the only and ultimate end contemplated by the Creator, in that sublime system of arrangement for life, which began with the morning of creation and ended with man. Nature is more than a cycle of change from dead matter to vegetable form, thence to animal life, and thence back again to mineral substance. Solomon wrote: “The dust shall return to the earth as it was, and the spirit shall return unto God who gave it;” and another has said: “There remains the paramount duty of rendering worthy of survival that spiritual part of our being which no merely physical power can destroy.” PHYSICS OF ORGANISMS. A brief discussion of some _physical_ characteristics of organisms will conclude our articles on “Home Studies in Chemistry and Physics.”