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. What are these substances and whence are they obtained? They consist of carbonate and phosphate of lime, principally, with small quantities of the sulphates of lime and magnesia, and a small percentage of other earthy matters. These substances are taken into the system in the food we eat and the water we drink, and it has been estimated that enough lime salts are taken into the system during an average lifetime to form a statue the size of the individual. Of course, the greater part is eliminated by the natural processes, but enough is retained to make ossification a formidable fact. Of the disastrous effects of a preponderance of these mineral salts in the system we have a notable example in the Cretins, a people in the Swiss Alps, who are the victims of premature ossification, their bodies being stunted, rarely attaining a greater height than four feet, and exhibiting all the signs of old age at thirty years; in fact, they seldom live longer than that. In this case the cause is directly traceable to the excess of calcium salts in the drinking water, for although heredity plays an important part in this matter, yet children from other parts, if brought into the region at an early age, soon manifest the symptoms and speedily become Cretins in fact. Most people are familiar with what is known among housewives as the formation of "fur" in the common tea kettle. This is nothing more nor less than the precipitation of the lime salts by evaporation. Four and five pounds' weight of this substance has been known to collect in this manner in a single vessel in twelve months. Many people are under the mistaken impression that boiling the water removes the lime. Not so. The precipitation only relates to that proportion of the water that has been evaporated; the remainder (in all probability) possesses a slightly higher percentage of solids than it originally did. So great is the proportion of mineral substance taken into the system in drinking water that it is safe to assert that, if after maturity was reached only distilled or other absolutely pure water was partaken of, life would be prolonged fully ten years. Up to the mature age it would be inadvisable, as the salts are necessary for bone formation. Good filtered rain water, or melted snow, are entirely free from mineral deposits, but if they have stood for any length of time it is advisable to boil them before using, to destroy any organic matter.