Reserve force is the energy which is stored in an organ or organism that is not required for normal functionating. Intelligent actions are the expressions of the sum total of life. This intelligence is able to accumulate and store energy derived from without. Certain fixed and definite conditions release this energy. The condition of an organ suitable for health is known as tone.
Tone consists of normal tension, normal firmness and normal renitency.
When nerves have the proper tension, the suitable solidity and the required resisting force, health is the result. Biology embraces a knowledge of living matter in contradistinction to substances which do not possess that vital force directed by an intelligence, a quality essential to intelligent beings. Physiology treats of the functions which create and continue a living existence, one which is normal, congenial and of health. Pathologic physiology is that condition in which the functions are performed abnormally. Pathology treats of the modifications of functions and the changes of tissue coincident therewith which always accompany the disturbance of functions.