DEDICATION. XV 



dustry, — it is the foundation of the riches of states. 

 But a rational system of Agriculture cannot be formed 

 without the application of scientific principles ; for 

 such a system must be based on an exact acquaintance 

 with the means of nutrition of vegetables, and with 

 the influence of soils and action of manure upon them. 

 This knowledge we must seek from chemistry, which 

 teaches the mode of investigating the composition and 

 of studying the characters of the different substances 

 from which plants derive. their nourishment. 



The chemical forces play a part in all the processes 

 of the living animal organism ; and a number of trans- 

 formations and changes in the living body are exclu- 

 sively dependent on their influence. The diseases in- 

 cident to the period of growth of man, contagion and 

 contagious matters, have their analogues in many 

 chemical processes. The investigation of the chemi- 

 cal connexion subsisting between those actions pro- 

 ceeding in the living body, and the transformations 

 presented by chemical compounds, has also been a 

 subject of my inquiries. A perfect exhaustion of this 

 subject, so highly important to medicine, cannot be 

 expected without the cooperation of physiologists. 

 Hence I have merely brought forward the purely 

 chemical part of the inquiry, and hope to attract at- 

 tention to the subject. 



Since the time of the immortal author of the " Ag- 

 ricultural Chemistry," no chemist has occupied him- 

 self in studying the applications of chemical principles 

 to the growth of vegetables, and to organic processes. 



