_Rice_ is rather meagre in nutriment; it contains but little phosphorous matter, with less carbon than other cereals, and is best and most generally employed as a diet in tropical countries. _Beans and Peas_ are rich in nutritious matter, and furnish the manual laborer with a cheap and wholesome diet. The _Potato_ is the most valuable of all fresh vegetables grown in temperate climates. Its flavor is very agreeable, and it contains very important nutritive and medicinal qualities, and is eaten almost daily by nearly every family in North America. Until very recently it, with the addition of a little butter-milk or skim-milk, constituted almost the sole diet of the Irish people. The average composition of the potato is stated by Dr. Smith to be as follows: Water 75 per cent., nitrogen 2.1, starch 18.8, sugar 3.2, fat 0.2, salts 0.7. The relative values of different potatoes may be ascertained very correctly by weighing them in the hand, for the heavier the tuber the more starch it contains. _Turnip and Cabbage_ are 92.5 per cent. water, and, consequently, poor in nutrition, though they are very palatable. The solid portions of cabbage, however, are rich in albumen. It is evident that the quantity necessary to maintain the system in proper condition must be greatly modified by the habits of life, the condition of the organism, the age, the sex, and the climate. The daily loss of substance which must be replaced by material from without, as we have seen, is very great. In addition to the loss of carbon and nitrogen, about four and a half pounds of water are removed from the system in twenty-four hours, and it is necessary that about this quantity should be introduced into the system in some form or other, however much it may be adulterated. Professor Dalton states: "From experiments performed while living on an exclusive diet of bread, fresh meat, and butter, with coffee and water for drink, we have found that the entire quantity of food required during twenty-four hours by a man in full health and taking free exercise in the open air is as follows: Meat, . . . . . . 16 oz., or 1.03 lb. avoir. Bread, . . . . . . 19 " 1.19 " " Butter or fat, . . . 3½ " 0.22 " " Water, . . . . . 52 fluid oz., 3.38 " " That is to say, rather less than two and a half pounds of solid food, and rather over three pounds of liquid food."