We are too wont to compare the working body with a machine, the boiler, engine, etc., overlooking the fact that the animal mechanism differs from the machine in at least one important respect. When we desire to set machinery in operation we must get up steam, and so a fire is started under the boiler and steam is generated in proportion as fuel is burned. The source of the energy made use of in moving the machinery is the extraneous combustible material introduced into the fire-box, but the energy of muscular contraction, for example, comes not from the oxidizable food material in the stomach, but from the material of the muscle itself. In other words, in the animal body it is a part of the tissue framework, or material that is closely incorporated with the framework, that is burned up, and the ability to endure continued muscular strain depends upon the nutritive condition of the muscles involved, and not upon the amount of food contained in, or introduced into, the stomach. All physiologists will, I think, acknowledge the soundness of this reasoning, but how few of us apply the principle in practice. It is perfectly logical to begin the work of the day with a comparatively empty stomach,—after we have once freed ourselves from the habit of a hearty breakfast,—and in the writer’s experience both mental and physical work have become the easier from this change of habit. The muscle and the brain are given opportunity to repair the waste they have undergone, by the taking of food at times when the digestive processes will not draw upon the energy that in activity is needed elsewhere.