One of the mysteries of physical life is hidden among these “lives”. Their action, forced forward by the Life energy—called _Prana_ or _Jiva_—will explain active existence and physical death. They are divided into two classes, one the destroyers, the other the preservers, and these two war upon each other from birth until the destroyers win. In this struggle the Life Energy itself ends the contest because it is life that kills. This may seem heterodox, but in Theosophical philosophy it is held to be the fact. For, it is said, the infant lives because the combination of healthy organs is able to absorb the life all around it in space, and is put to sleep each day by the overpowering strength of the stream of life, since the preservers among the cells of the youthful body are not yet mastered by the other class. These processes of going to sleep and waking again are simply and solely the restoring of the equilibrium in sleep and the action produced by disturbing it when awake. It may be compared with the arc-electric light wherein the brilliant arc of light at the point of resistance is the symbol of the waking active man. So in sleep we are again absorbing and not resisting the Life Energy; when we wake we are throwing it off. But as it exists around us like an ocean in which we swim, our power to throw it off is necessarily limited. Just when we wake we are in equilibrium as to our organs and life; when we fall asleep we are yet more full of life than in the morning; it has exhausted us; it finally kills the body. Such a contest could not be waged forever, since the whole solar system’s weight of life is pitted against the power to resist focussed in one small human frame. The body is considered by the Masters of Wisdom to be the most transitory, impermanent, and illusionary of the whole series of constituents in man. Not for a moment is it the same. Ever changing, in motion in every part, it is in fact never complete or finished though tangible. The ancients clearly perceived this, for they elaborated a doctrine called Naimittika Pralaya, or the continual change in material things, the continual destruction. This is known now to science in the doctrine that the body undergoes a complete alteration and renovation every seven years. At the end of the first seven years it is not the same body it was in the beginning. At the end of our days it has changed seven times, perhaps more. And yet it presents the same general appearance from maturity until death; and it is a human form from birth to maturity. This is a mystery science explains not; it is a question pertaining to the cell and to the means whereby the general human shape is preserved.