I feel that I cannot begin this chapter better than by quoting what Dr. Letheby says on the subject:

"Primarily, all our foods are derived from the vegetable kingdom, for no animal has the physiological power of associating mineral elements and forming them into food. Within our own bodies there is no faculty for such conversion; our province is to pull down what the vegetable has built up, and to let loose the affinities which the plant has brought into bondage, and thus to restore to inanimate nature the matter and force which the growing plant had taken from it."

It is thus plain that the beef and mutton we eat derive their fibrine, gluten, and all other necessary ingredients from the vegetables on which the oxen and sheep have fed, though such food does not apparently contain any of these substances. It is a curious suggestion which I have often met with, that if a vegetarian family lived in accordance with the rules of one of their own peculiar cookery books, each member would actually consume half an ounce more animal food a day than a man would do who lived according to the usual scale of diet.

Vegetables are aliments which dilute the blood, and contain more salts than albumen. They convey very little nutriment to the blood, as we may see in the feeble muscles of tropic-dwellers who feed almost entirely on vegetables. On the other hand, they are of great service, first in the digestive canal, where they dissolve the albuminous substances of the meat, and afterwards in the blood itself, where, if they do not actually nourish, they yet keep the albumen and fibrine in a liquid state, and enable those substances to perform their proper functions more vigorously. Of course the cereals would naturally stand first in a chapter on vegetables, as they, of all the products of the vegetable kingdom, are the most depended upon by man for food. As, however, wheat, which is the principal cereal of England, has been noticed in another chapter, we may as well proceed to examine the nutritive properties of other vegetables. In such an inquiry the potato comes first, for, owing to its large proportion of starch, it is the most actually nourishing of all vegetables. This starch is transformed into fat by the digestive process, and if potatoes could be eaten with a sufficiency of white of egg, their nutritive value would be brought very near the meat standard. Other roots and tubers contain a larger proportion of sugar, and there is even fat present in some of them, but none are so rich in this nourishing starch as the potato. A man may, and probably will, look fat and rosy on a potato diet, yet his muscle will not be in first-rate condition, nor will he be able to endure prolonged fatigue. In spite, therefore, of the comparative low price of potatoes, they are not the most economical food for a labourer, nor can he depend on their nourishing starch alone to provide him with the requisite bodily strength. All succulent vegetables are anti-scorbutic, and since the potato was brought into use as a daily ration in the fleet (not a hundred years ago), scurvy has gradually died out. If there is any difficulty in providing potatoes - for during long voyages, when crossing the tropics, the potatoes will begin to grow, and so become unfit for food - lime-juice is the next best substitute, for it contains most of the chemical ingredients which go to make the salts of potash found in all fresh vegetables, but which is specially present in the potato. It has often been pointed out that there is really no excuse for scurvy now-a-days, for potatoes, cabbages, turnips, and carrots can be pressed into a very small space, and yet carry their potash about with them. Indeed, this process has lately been carried to great perfection. Other vegetables are less actually nutritious than the potato, and the palate grows sooner tired of them, but yet one hundred pounds of potatoes contain barely as much nitrogenous matter, - that is to say, positive nourishment, - as thirteen pounds of wheat.

As the wholesomeness and digestibility of vegetables depend much on how they are cooked, it is perhaps useless to enter here into a longer explanation why vegetables, though they constitute the entire food of animals whose flesh contains the highest forms of nourishment, will not, of themselves, supply man with the food he requires to keep his muscles strong and vigorous. In the countries where the inhabitants are compelled by the necessities of the climate to live chiefly on them, Nature is so bountiful that she does not call upon man to cultivate the ground as we are obliged to do. Therefore, it stands to reason that in a climate where severe manual labour is necessary to produce food, a diet of a muscle-relaxing, fat-forming nature is a very poor economy.