TO THE TEACHER xiii 



from the references cited in the Appendix. Here also will be found 

 tables of digestible nutrients, and other data useful for instruction. 

 The author has departed from the usual custom of placing 

 questions and exercises at the end of the chapters. A careful 

 inquiry into the matter has seemed to indicate that neither ques- 

 tions nor exercises are much used. Most teachers prefer to for- 

 mulate their own questions and topics, and to prepare their own 

 laboratory exercises, or to use prepared exercises in which are 

 fuller directions for work than can be given in a textbook. 



BENJAMIN MARSHALL DAVIS. 

 OXFORD, OHIO, 

 February i, 1922 



