SALICYLIC ACID AND SALIC YLATES. 755 



normal and lethal dose of a food and a drug, or, as in this case, a 

 chemical preservative. The chart shows two curves, one representing a 

 chemical preservative and one representing a food. The normal dose 

 of a food is that quantity of food which maintains a healthy adult body 

 in equilibrium. It is represented on the right of the chart by the 

 number 100. If the quantity of food necessary to maintain the equi- 

 librium in a healthy adult body is slightly diminished, no apparent 

 change is at first experienced and possibly even no discomfort. If, 

 however, the quantity of food be still further diminished progressively, 

 as indicated by following the curve down to the left, the point is 

 finally reached when no food is given at all and death ensues, repre- 

 sented by zero on the left-hand of the diagram designated "lethal 

 dose." As the curve begins to deviate from the perpendicular .on the 

 right the degree of injury is very readily noticed and starvation or 

 symptoms of starvation are set up. Thus, if you follow the perpen- 

 dicular on the right downward to the point 80, the divergence of the 

 corresponding point of the curve is already measurable. As } T ou 

 descend to zero the magnitude of the measurement increases. It re- 

 quires 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. 



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 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 ordi- 

 nary 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 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 is, it will 

 still produce an injurious effect, which may be infinitely small if the 

 dose be infinitely small. It follows then, as a mathematical demonstra- 

 tion, that any quantity of an injurious substance added to a food 

 product must of necessity be injurious, provided it is in the nature of 

 a drug and the body is in a perfectly healthy normal condition. 



Hence the argument which has been so persistently urged in favor 

 of a chemical preservative that if in small quantities it is harmless is 

 shown to be wholly untenable. Where there is no necessity for the 

 addition of a harmful substance, where no particular benefit is secured 

 thereby, and where there is no disturbance of the normal state of 



