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INTRODUCTION 



That part of Agricultural Chemistry which we may term 

 Organic has to do with living plants and animals. Considered 

 agriculturally as farm products, animals and plants have three 

 general uses : (i) as servants of man in performing work, (2) as 

 food for animals including man, (3) as material, or for furnish- 

 ing material for the use of man in other ways than as food. A 

 knowledge of the chemistry of plants and animals is of value 

 in understanding th^ir uses in these various ways and in showing 

 how their economic value may be increased by greater produc- 

 tion, greater conservation or the development of new uses. 



The chemistry of living organisms is termed bio-chemistry ^' 

 and as a whole includes all of their physico-chemical relation- 

 ships, especially those connected with the inorganic soil food of 

 plants. This latter part of bio-chemistry we shall not consider, 

 as it belongs to the inorganic division of agricultural chemistry. 



The present study will treat of the composition of plants and 

 animals and later of the physiological processes by which their 

 body substance is built up and the energy of their living pro- 

 cesses is produced. It will thus be largely physiological, with 

 especial attention to the general subjects of food and nutrition 

 and photosynthesis. 



In order to understand the composition of plants and animals 

 and the chemical reactions involved in their living processes, it 

 is necessary to know the nature of the individual compounds of 

 which they are constituted. As the greater part of these are 

 what we term organic, and as these alone are related directly 

 to the energy of the living organism, we shall take up first a 

 brief study of systematic organic chemistry, discussing only such 

 compounds as are directly related to agriculture. 



We shall then be in a position to study the fundamental 

 processes and reactions of living things and those particular 

 physiological processes which differentiate plants from animals. 



