What is the proper food of man?--Food to be adapted to constitution and circumstances--Diet must vary with time of life--Diet in infancy--The mother’s milk the best--Substitutes for it.--Over-feeding a prevalent error--Causes which vitiate the quality of the milk--Regimen of nurses--Weaning--Diet after weaning--Too early use of animal food hurtful--Diet of children in the higher classes too exciting--and produces scrofula--Mild food best for children--Incessant eating very injurious--Proper diet from childhood to puberty--It ought to be full and nourishing but not stimulating--Often insufficient in boarding-schools--Diet best adapted for different constitutions in mature age--Regimen powerful in modifying the constitution, mental as well as physical--Farther investigation required. The next question which presents itself is, What is the proper food of man? In answering it, we must begin by making distinctions, otherwise we shall, in the very outset, fall into error. On examining the structure of the human body at different ages, and in different individuals, remarkable differences are observable in the relative proportions of the elements or tissues of which it is composed. In one, the muscular system predominates, and the body is remarkable for a compactness of fibre indicative at once of strength and activity. In another, the lymphatic system is the most conspicuously developed, and its features are easily recognised by the full, soft, and rounded form, and languid action, which generally accompany it. In a third, the thin and sharp outline, irregular and vivacious activity, and great susceptibility of impressions, betoken the predominance of the nervous over all the other functions; while, in a fourth, the florid complexion, expanded chest, and general vivacity of disposition, as clearly point out the superior development and energy of the vascular system. Such are the four principal constitutions, long familiarly known under the names of the _bilious_, the _lymphatic_, the _nervous_, and the _sanguine_ temperaments. Very frequently the habit of body indicates a mixture of two or more of these temperaments, in which case the results of course are modified according to the proportions in which they are combined.