AND ITS RELATION TO ANIMAL LIFE 17 



that these variations or deficiencies are in the 

 main the predisposing cause in many diseases. 

 In the following pages I shall try to show 

 in a more or less detailed way how the quality 

 of the food is governed by the mineral con- 

 stituents present in or absent from the soil, how 

 the variations in plant food affect the immunity 

 or otherwise of the animal living on it, and 

 how these variations, either directly or through 

 the animal, affect man. 



