tion of the skin secretion should be primary in connection with this question.
Seeing that this has been entirely neglected, I am justified in expressing, very plainly and positively, my opinion of the worthlessness of all the modern research upon which the alleged refutation of Liebig's theory of the destruction and renewal of living tissue in the performance of vital work is based, and my rejection of the modern alternative hypothesis concerning the manner in which food supplies the material demanded for muscular and mental work.
I may be accused of rashness and presumption in thus standing almost, if not quite, alone in opposition to the overwhelming current of modern scientific progress. Such, however, is not the case. It is modern scientific fashion, rather than scientific progress, that I oppose. We have too much of this millinery spirit in the scientific world just now; too much eagerness to run after "the last thing out," and assume, with undue readiness, that the "latest researches" are, of course, the best—especially where fashionable physicians are concerned.
XLIX.—THE MODERN THEORY OF FOOD.
In my last I summarized Liebig's theory of the source of vital power, and its supposed refutation by modern experiments, but had not space to state the substituted theory. I will now endeavor to do so, though not without difficulty, nor with satisfactory result, seeing that the recent theorists are vague and self-contradictory. All agree that vital power or liberated force is obtained at the expense of some kind of chemical action of a destructive or oxidizing character, and is, therefore, theoretically analogous to the source of power in a steam engine; but, when they come to the practical question of the demand for working fuel or food, they abandon this analogy.
Pavy says ("Treatise on Food and Dietetics," page 6): "In the liberation of actual force, a complete analogy may be traced between the animal system and a steam-engine. Both are media for the conversion of latent into actual force. In the animal system, combustible material is supplied under the form of the various kinds of food, and oxygen is taken in for the process of respiration. From the chemical energy due to the combination of these, force is liberated in an active state; and besides manifesting itself as heat, and in other ways peculiar to the animal system, is capable of performing mechanical work." In another place (page 59 of the same work), after describing Liebig's view, Dr. Pavy says: "The facts which have been already adduced (those described in my last paper) suffice to refute this doctrine. Indeed, it may be considered as abundantly proved that food does not require to become organized tissue before it can be rendered available for force-production." On page 81 he says: "While nitrogenous matter may be regarded as forming the essential basis of structures possessing active or living properties, the non-nitrogenous princi-
