It is a matter of great importance that their diet, clothing and habits be regulated by certain laws, which will, to a great extent, reduce the dangers to which they are exposed in the discharge of their duties. DIET. Man is less uniform in his diet, and suffers more in consequence of it, than any other animal. All other animals are directed by instinct to select only those substances which are best adapted to their wants. Man is endowed with reason to enable him, by the exercise of thought and reflection, to make his choice of food. He should, therefore, select his daily food with as much forethought and care as he would select the materials for his dwelling. He should consider, not what will gratify his taste, but what will build up and strengthen his bodily structure, and secure most perfectly the highest and most permanent enjoyment of all his faculties. The kind of food which each individual should select is by no means uniform; the climate, the season of the year, the occupation, the temperament, the age, the habits of life, and various other circumstances which might be mentioned, demand modifications of diet. MODIFICATIONS OF AGE. The constituent elements of the body are not found in the same relative proportions at different periods of life, or in different individuals of the same age. In middle life the muscular system predominates, and the body is remarkable for the compactness of its fibres, its strength, and its power of endurance. In the child there is an excess of fluids, which renders the body more plump and round and the form beautiful, though more frail and delicate than at a later period. In advanced age, the soft tissues become greatly diminished, and the form wrinkled and wasted. CLIMATE. The inhabitants of cold climates require those articles of food which produce the largest amount of animal heat, such as oil, tallow and fat meats, which contain from sixty-six to eighty per cent. of carbon. The natives of the arctic regions consume enormous quantities of fat and oil, and seem to relish them as great luxuries; the inhabitants of tropical regions subsist mainly on rice, fruits, vegetables and lean meats. It would be impossible to live in Greenland on the plaintain and rice of the Hindoo, or in Hindostan on the seal fat and whale oil of the Greenlander. In temperate climates we require different kinds of food at different seasons of the year. In winter we consume larger quantities of fat meat and carbonaceous food, and in summer more fruit and vegetables. Were we to indulge in the summer in the same diet which we might find highly conducive to health in the winter, the system would soon become burdened with an excess of carbonaceous matter, and induce congestion and inflammatory diseases. It is therefore highly important that each person should possess some knowledge of the properties of different articles of diet, and select from time to time those which he may think most suitable to his own organization.