INTRODUCTION 



In this book I have endeavoured to provide a general 

 introduction to the science of growing crops and feeding 

 animals : an outline, in fact, of the theory of the nutri- 

 tion, first of the plant and then of the animal. The book 

 is intended on one side to give the student of agriculture 

 a general framework of ideas, before he enters upon the 

 more detailed study of agricultural chemistry that will 

 be presented to him by his professor. I have found that 

 such students often experience a difficulty in following and 

 making the best use of their lectures because the whole 

 trend of the subject is strange to them ; they would 

 be better able to appreciate the value of the illustrations 

 they receive if they could at once see their bearing upon 

 the scheme of nutrition of plant or animal. There are 

 many students also in our schools and colleges who do 

 not as a rule pursue the subject any further than it is 

 carried in these pages ; both on their account and for 

 the student who is only laying a foundation, I have 

 insisted as far as possible on the main principles govern- 

 ing this branch of science, hoping thereby to induce a 

 sound way of thinking that will not prove misleading on 



