It is to be remembered that the advance of civilization, and the facilities of transportation and cold storage, have brought from far and near an innumerable number and variety of articles for food and drink, including condiments, which bear no relation to the few simple articles formerly consumed; even the fruits which we eat are rarely ripened fully by nature, but are picked more or less green, and undergo an artificial ripening without the action of the sun, which is really akin to decay. In the combination and preparation of articles of food also, so-called civilization and refinement have made the greatest departure from the simple life of the aborigines, who are free from cancer, and with increasing ease and wealth throughout the civilized world more and more individuals are sharing in unnecessary and often harmful indulgences, more and more freely: and this is especially true of animal food, the consumption of which has increased so greatly. Many other elements likewise enter into the matter of the digestibility and consequent nutritive power of food and drink; such are nervous conditions, rapid eating, imperfect mastication and insalivation, heat and cold, character of the air breathed, micro-organisms, etc., and all the various causes which may derange the action of the digestive organs and so prevent the perfect metabolism between nutrient material and the cells of the body, as I tried to show you in some former lectures. As is well known, the nutrition of man is supplied by the organic substances, protein, carbohydrates, and fat; these are found in various combinations in animal and vegetarian foods, and as a rule contain also much of the inorganic or mineral substances necessary for the system; all of these with water, and its salts, and oxygen, supplied by the lungs, unite, through anabolism and catabolism, to build and maintain the human body in health. It is also well known that in order to preserve health and proper weight there must exist in the economy a certain balance or equilibrium between the amount of the ingesta and excreta, representing the various elements which enter into nutrition; thus we speak of a nitrogen equilibrium, a carbo-hydrate equilibrium, a phosphorus equilibrium, and iron equilibrium, etc., some of which are disturbed continually in ill health and in various diseases, including cancer, as has been shown in our last lecture.