igo8. 



UPON HEALTH AND METABOLISM. 



327 



a food can be measured immediately after the curve begins to vary 

 appreciably from the perpendicular on the right. 



Let us now consider the perpendicular on the left, which is 

 marked at the top under the term " lethal dose," viz. ; a quantity of 

 the added preservative sufficient to destroy life. The normal dose of 

 such an added chemical preservative is o, 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 



LETHAL DOSE 

 lOO-i 



NORMAL DOSE 



LETHAL DOSE " J" 75 mffMAL DOSE 



Fig. I. Graphic chart representing the comparative intluences of foods 



and preservatives. 



so slightly from the horizontal base as to be impossible of measure- 

 ment 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 o 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 pre- 

 servative is, it will still produce an injurious efifect, which may be 

 infinitely small if the dose be infinitely small. It follows then, as a 



