xvi INTRODUCTION 



and tradition. The day is approaching when this 

 must be changed and the teaching of Experimental 

 Science must be listened to even in Agriculture if we 

 are to bear the burden of supporting the enormous 

 and ever-growing populations of to-day. Personally 

 I have little doubt of success in this direction. 

 Improved methods will here have less to fear from 

 that which, especially in England, is their most for- 

 midable enemy in the industrial world, namely the 

 inertia of capital. It requires no elaborate plant 

 to enable the farmer to use a pure pedigree wheat 

 in his fields and to guide his choice of manures by 

 sound principles. That he is naturally conserva- 

 tive in his methods is a necessity of his art but 

 when better methods are brought to his knowledge 

 which are supported by practical demonstrations 

 such as those set out in these Essays the force of 

 which, he, of all men, is best capable of appreciat- 

 ing I have little fear that he will not shew himself 

 willing to learn. 



I have more doubt of the prompt acceptance of 

 the new teaching as to Disease. Medical Practice 

 has for so many ages rested on empiricism and tra- 

 dition and has been so completely dominated by 

 authority that it is hard for it to give a speedy 

 welcome to new knowledge. Fortunately the invasion 

 has already been so successful that so far as Causes 

 are concerned the victory is gained. No one refuses 

 to accept the existence and effects of Pathogenic 

 Bacteria or Protozoa. But there is and must for 



