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perpendicular on the right downward to the point 80 the divergence of the corresponding point of the curve is already measurable. As you descend to 0 the magnitude of the measurement increases. It requires but very little further illustration to show how easily the effect of diminishing the normal dose of a food can be measured immediately after the curve begins to vary appreciably from the perpendicular on the right.

Fig. 7.—Graphic Chart Representing the Comparative Influences of Foods And Preservatives.

Let us now consider the perpendicular on the left, which is marked at the top under the term "Lethal dose," namely, a quantity of the added preservative sufficient to destroy life. The normal dose of such an added chemical preservative is 0 and is shown at the base line to the right, marked "Normal dose." If you add a very minute quantity of a chemical preservative, the curve representing it varies so slightly from the horizontal base as to be impossible of measurement by ordinary means. If we follow along to the number 75 on the horizontal base we see the deviation of the curve is sufficiently great to measure. At 50 it is still greater, at 25 still greater, while at the left of the basic line it is a maximum extending from 0 to 100, or the lethal dose. It is easy to show by mathematical data that no matter how small the quantity of an injurious substance or preservative it will still produce an injurious effect which may be infinitely small if the dose be infinitely small. It follows, then, as a mathematical demonstration that any quantity of an