[12] The word "Vegetarianism" implies a judgment of the qualities which such a diet entails. This word is derived, in fact, from the Latin adjective "Vegetus" (strong). The word "Vegetalism," which we oppose to the preceding one, admits only the establishing of a fact, that of the choice--exclusive or preferred--of the nutritious matters in the vegetable kingdom. II Before putting "vegetalism" into practice the first point is to know whether the foods of "vegetal" origin contain, and are susceptible of producing regularly, the divers nutritive principles indispensable to the organisation of an alimentary diet. The principles are the following:--Proteid or albuminoid substances; hydrocarbonated and sweet substances fatty substances; mineral matters, alkalis, lime, magnesia, phosphates and chlorides, etc. In most compound foods, no matter of what origin, mineral materials almost always exist in sufficient quantities. The most important amongst them, at all events, are found combined in liberal, even superabundant, portions in dishes of vegetal origin. The analysis of the ashes of our most common table vegetables fixes us immediately to this subject: Leguminous plants supply from about three to six per cent. of ashes, rich in alkalis, lime and phosphates. Potatoes, green vegetables and fruit as a whole absorbing considerable quantities of mineral elements. These are the elements of a nature to allow a precise reply to this question which we propose to expound briefly. III In order to examine a food thoroughly, for the purpose of ascertaining if it can be advantageously introduced for consumption, whether albumins, fats, hydrate of carbon, or sugar, etc., or again an association of these principles in a composite article of food are in question, divers researches must be carried out before giving a final judgment. If a more or less complex article of food is in question, before considering it as a good nutriment, its centesimal composition, or its immediate composition, should be established; its theoretic calorific power should be known, and it should be measured if this has not yet been done. Besides the calorific yield thus estimated _in vitro_, the real utilisation in the human organism of articles of food alone or mixed with other foods should be determined, taking simultaneously into account their effects, whether tonic, stimulating or depressing. From a different point of view it is no longer allowable to neglect before judging whether such and such a nutritive substance is advantageous, the valuation of what we have called, with Prof. Landouzy, the economic yield--that is to say, the price of the energy, provided by the unity of weight of the article of food. It is only in reviewing "vegetal" substances, taking these divers titles into consideration, that we shall be justified in attributing to the practice of "vegetalism," integral or mitigated, its definite value. IV