direction given to this food force, as every movement of the hand on the dial is but the manifestation of the power of the bent spring in the watch. We use the pent-up energies of meat, bread, and vegetables which are placed at our service, and transfer them to a higher theater of action. [Footnote: It is a grand thought that we can thus transform what is common and gross into the refined and spiritual; that out of waving wheat, wasting flesh, running water, and dead minerals, we can realize the glorious possibilities of human life.] KINDS OF FOOD NEEDED.--From what has been said it is clear that, in order to produce heat and force, we need something that will burn, _i. e._, with which oxygen can combine. Experiment has proved that to build up every organ, and keep the body in the best condition, we require three kinds of food. 1. _Nitrogenous Food_.--As nitrogen is a prominent constituent of the tissues of the body, food which contains it is therefore necessary to their growth and repair. [Footnote: Since this kind of food closely resembles albumen, it is sometimes called _Albuminous_. The term Proteid is also used.] The most common forms are whites of eggs--which are nearly pure albumen; casein--the chief constituent of cheese; lean meat; and gluten--the viscid substance which gives tenacity to dough. Bodies having a great deal of nitrogen readily oxidize. Hence the peculiar character of the quick-changing, force-exciting muscle. 2. _Carbonaceous Food_--_i. e._, food containing much carbon-- consists of two kinds, viz., the _sugars_, and the _fats_. (1) The _sugars_ contain hydrogen and oxygen in the proportion to form water, and about the same amount of carbon. They may, therefore, be considered as water, with carbon diffused through it. In digestion, starch and gum are changed to sugar, and so are ranked with this class. (2) The _fats_ are like the sugars in composition, but contain less oxygen, and not in the proportion to form water. They combine with more oxygen in burning, and so give off more heat.