Vlll PREFACE 



physiological, and centers around the general subjects of food 

 and nutrition as applies to both animals and plants and photo- 

 synthesis in plants. In the last section on Crops, Foods and 

 Feeding the effort has been to present the chemical basis for 

 the valuation of animal foods, but without entering into the dis- 

 cussion of the practical operation and results of animal feeding. 



In presenting the physiological chemistry of plants and ani- 

 mals a departure has been made from the usual custom, and the 

 detailed study of animals and animal nutrition is considered 

 before that of plants. The author believes that this procedure 

 presents bio-chemistry in such a way that the student gains the 

 correct view of plants and animals as living organisms. It also 

 emphasizes the real differences between these two forms while 

 retaining the idea of fundamental similarity. 



There has been no effort to make the book a handbook of 

 facts in regard to the subjects treated, and it is not a textbook 

 of agricultural analysis, the methods mentioned being consid- 

 ered only as to the fundamental principles. The presentation is 

 general and is in the lecture style with the underlying purpose 

 of making a book of the most value to students as a text for 

 class use. Laboratory experiments have been incorporated in 

 the text as this has seemed to be desirable. Except in connec- 

 tion with the tables practically no references to literature have 

 been cited, but at the end of each section a list is given of 

 reference books which cover the subjects discussed. The author 

 wishes to give full credit to all of these books as sources of the 

 material presented. 



The book is the result of five years' experience in giving a 

 course in general agricultural chemistry to students in practical 

 agriculture and horticulture in the Massachusetts Agricultural 

 College, the work in the present volume being carried in a 

 course of two lectures and one laboratory per week for one 

 semester. 



While intended primarily for use in Agricultural Colleges, the 

 author hopes that the book may be found of value in other 

 colleges where an elementary presentation of bio-chemistry is 

 desired. 



