shall not dwell unduly upon this point, in this place; partly because Dr Rabagliati and myself are, as yet, practically alone in our belief that the energy of the body does not come from the food; and partly because this book is devoted to the _quality_ of the various foods, rather than to their _quantity_—as was my former book. Both—quantity and quality—are of great interest and importance; but as I have already said all that is necessary regarding one aspect of this question—that of quantity—I feel that a somewhat detailed discussion of the “quality” of food could not fail to be of interest. I accordingly turn to this aspect of the problem; and shall devote the remaining pages of this book to a discussion of the relative qualities and proportions of the various foods. [1] “Vitality, Fasting and Nutrition.” [2] At first sight this position seems, of course, absurd, and opposed to the well-known facts of calorimetry: but such is not the case. All the known facts as to the equivalence of energy, heat, work, etc., can be accounted for just as readily on my theory of the relations of food and bodily energy—viz. that the energy is restored by sleep (the nervous system, like an electric motor) and not by combustion, as in the steam engine. As to the equivalence noted, this can be accounted for by assuming that as energy acts upon matter, it wastes; and this waste is made good by a proportionate amount of food. There is therefore an equivalence, a relation, but it is not that of cause and effect. For the details of this theory, however, see “Vitality, Fasting and Nutrition,” pp. 225-303 _et seq._ necessary by the various physiologists. The truth of the matter doubtless is, that the _smallest_ amount of food is that which is necessary, and all amounts over and above this are passed through the body at an expense of the vital energies, and to the detriment of the vital economy. However, I shall not dwell unduly upon this point, in this place; partly because Dr Rabagliati and myself are, as yet, practically alone in our belief that the energy of the body does not come from the food; and partly because this book is devoted to the _quality_ of the various foods, rather than to their _quantity_—as was my former book. Both—quantity and quality—are of great interest and importance; but as I have already said all that is necessary regarding one aspect of this question—that of quantity—I feel that a somewhat detailed discussion of the “quality” of food could not fail to be of interest. I accordingly turn to this aspect of the problem; and shall devote the remaining pages of this book to a discussion of the relative qualities and proportions of the various foods. II THE ARGUMENT FROM COMPARATIVE ANATOMY