What is termed old age is simply ossification (solidification of the tissues), and this is due to the constant deposition in the system of earthy substances. The result of these deposits being retained in the system is: that there is an excess of mineral matter in the bone tissue, which renders it brittle, and accounts for the susceptibility to fracture in advanced life; it causes a change in the structure of all the blood vessels, great and small, thickening their walls and thus reducing their calibre and also rendering them brittle. With diminished capacity the blood vessels fail to convey the requisite nutrition to the tissues, and a general lowering of the vitality follows. The capillaries no longer supply the skin with its needed pabulum, hence it loses its elasticity and color--grows yellow and forms in furrows. The circulation being sluggish, the deposition of these earthy substances in the neighborhood of the various joints and the muscular structures is facilitated, and we have the stiffness of joints and muscular pains that usually accompany age. The supply of blood to the brain and nerve substance is curtailed in the same manner, and for lack of sustenance these structures commence to decay, which accounts for diminished mental activity and sensory impressions. As the process continues there may be almost complete obliteration of the capillaries, while the larger vessels may become so thickened that their capacity is sometimes reduced three-fifths. Then comes death. Then, since old age is due to the cause just described, it follows, as a perfectly logical deduction, that if we can prevent the introduction of these substances into the system, or even check them, then the duration of life and preservation of function should be proportionately prolonged.