The reader may naturally suppose “that the readiness with which the gastric fluid acts on the several articles of food, is in some measure determined by the state of division, and the tenderness and moisture of the substance presented to it,” and he may also be aware of the fact, that the readiness with which any substance is acted upon by the gastric juice, does not necessarily imply that it possesses nutritive characteristics, for it stands to reason that a substance may be nutritious, and yet hard to digest; and when this is the case, the gastric follicles supply a greater quantity of fluid, in order to effect the conversion of the food into chyme. Pepsine and the hydrochloric acid, the two indispensable and inseparable solvents, are consequently secreted in greater abundance in order to meet and overcome the difficulty, so that the food may be in a condition fit for assimilation with the various tissues. Man requires a mixed kind of aliment, therefore he must have animal as well as vegetable food, though there are many instances of people who live wholly on animal or vegetable substances; these of course are anomalies, and therefore their habits are unnatural. Vegetarianism is a foolish freak of the weak-minded and semi-ignorant; the structure of the teeth of man points conclusively to the fact that he is both carnivorous and herbivorous; though these vegetable philosophers would have us believe that he is destined to feed upon cabbages! Food is divided into two groups, nitrogenous and non-nitrogenous, or animal and vegetable; the only non-nitrogenous organic substances of the animal, or nitrogenous, are furnished by the fat, and in some few cases by those vegetable matters that may happen to be in the organs of digestion of those animals who are eaten whole. Nutritive or plastic, is given to those principles of food which are converted into fibrine or albumen of blood, and being assimilated by the various tissues through its medium, and those principles comprising the major part of the non-nitrogenous food, in the form of fat, gum, starch, and sugar, and other substances of a similar nature, are supposed to be utilised in the production of heat, and are termed calorifaciant, or sometimes respiratory food. The principal ordinary articles of vegetable food contain identical substances, in composition, with the fibrine, caseine, and albumen, which constitute the chief nutritive materials of animal food; for instance, the gluten which is present in corn is identical in composition with fibrine, and is therefore called vegetable fibrine; legumen, which exists in beans, peas, and other seeds of the leguminosæ, is similar to the caseine of milk; and albumen is most abundant in the seeds and juices of nearly all vegetables.