The total cycle of energy from the start of storage to the end of liberation of energy, starting once more with the storing of energy, may be regarded as the cycles of organic functional activity which is classified under metabolism. We deal here with a reservoir of vital energy whose life activities or reactions depend on the amount of energy contained in the cell or the neuron, and whose functioning and reactions vary with the level of energy in the reservoir. The neuron is but a highly differentiated cell or reservoir for the intake and outgo of energy. In this respect the nerve cell is entirely like other cells of humbler function. Every cell is a storage cell, accumulating energy and then liberating it at an appropriate occasion of a given stimulus, all cells working for the preservation of the organism as a whole. The rise and fall of the level of energy in the reservoir regulate the various manifestations, sensory, motor, emotional, mental which the individual displays to the various stimulations coming from his environment. Within certain limits the fall of energy is normal,--when it reaches a certain level the organism once more replenishes the store and once more the level of energy rises. This energy is _Dynamic_ under certain conditions. However, the discharge of energy must go on, and the organism must draw further on its store of energy, on the accumulated store of energy put away for safety and emergency. This stored up energy is _Reserve Energy_.[16] The late Charles S. Minot, the American histologist, points out this reserve energy present in the organism, a reserve energy of growth called forth under special emergencies of life. By a striking series of instructive facts, Dr. Meltzer points out that “all organs of the body are built on the plan of superabundance of structure and energy.” Like Minot, Meltzer refers to the significant fact that most of our active organs possess a great surplus of functioning cells. This surplus is requisite for the safety of the individual. If, however, the drain of energy still goes on without replenishing the total store, the energy drawn on the region of the danger zone is entered. _This energy is Static._ The concomitant symptoms are various psychomotor and psycho-secretory disturbances of a psychopathic or psycho-neurotic character. This energy is drawn from the upper levels of energy. Under such conditions restitution of the total amount of energy to its normal level is still possible. Should the process of liberation of energy go on further without restitution, the energy drawn is taken from the lower levels of static energy, and the symptoms are _functional_, _neuropathic_. The lower-most levels of static energy are the last the cell can dispense with to save itself from total destruction. With further increase of discharge of energy the cell must give its very life activity, the energy is drawn from the breaking up of cell tissue; this energy is organic or necrotic.