These four lower material constituents are transitory and subject to disintegration in themselves as well as to separation from each other. When the hour arrives for their separation to begin, the combination can no longer be kept up, the physical body dies, the atoms of which each of the four is composed begin to separate from each other, and the whole collection being disjointed is no longer fit for one as an instrument for the real man. This is what is called “death” among us mortals, but it is not death for the real man because he is deathless, persistent, immortal. He is therefore called the Triad, or indestructible trinity, while they are known as the Quaternary or mortal four. This quaternary or lower man is a product of cosmic or physical laws and substance. It has been evolved during a lapse of ages, like any other physical thing, from cosmic substance, and is therefore subject to physical, physiological, and psychical laws which govern the race of man as a whole. Hence its period of possible continuance can be calculated just as the limit of tensile strain among the metals used in bridge building can be deduced by the engineer. Any one collection in the form of man made up of these constituents is therefore limited in duration by the laws of the evolutionary period in which it exists. Just now, that is generally seventy to one hundred years, but its possible duration is longer. Thus there are in history instances where ordinary persons have lived to be two hundred years of age; and by a knowledge of the occult laws of nature the possible limit of duration may be extended nearly to four hundred years. { Brain, { Nerves, The visible { Blood, physical { Bones, man is: { Lymph, { Muscles, { Organs of Sensation and Action, { and Skin, The unseen { Astral Body, physical { Passions and Desires, man is: { Life Principle, (called _prana_ or _jiva_.) It will be seen that the physical part of our nature is thus extended to a second department which, though invisible to the physical eye, is nevertheless material and subject to decay. Because people in general have been in the habit of admitting to be real only what they can see with the physical eye, they have at last come to suppose that the unseen is neither real nor material. But they forget that even on the earth plane noxious gases are invisible though real and powerfully material, and that water may exist in the air held suspended and invisible until conditions alter and cause its precipitation.