TO THE TEACHER xiii 



lists, you should get, through your congressman, the yearbooks 

 of the Department of Agriculture, the annual reports of the 

 Surgeon-General of the Public Health Service, and the annual 

 reports of the Smithsonian Institution. State agricultural ex- 

 periment stations, state and local boards of health, state and 

 other museums, and the larger insurance companies also issue 

 publications of value to the students of biology. Several of the 

 larger voluntary health organizations have in recent years come 

 to cooperate in some of their administrative problems, and can 

 all be reached at one address — 370 Seventh Avenue, New York. 

 Most of the following organizations have available literature of 

 value in the teaching of biology: the American Child Health 

 Association ; American Heart Association ; American Social Hy- 

 giene Association ; American Society for the Control of Cancer ; 

 National Committee for ]\Iental Hygiene ; National Tubercu- 

 losis Association; American Association for Medical Progress; 

 American Committee for the Prevention of Blindness. Some of 

 the most helpful material is to be found in current magazines 

 and newspapers, and pupils should be encouraged to find both 

 problems and applications in the current record of the human 

 life about them. 



The classification of plants and animals appeals to individuals 

 here and there, but we cannot afford to give it too much time as 

 a branch of biology. Yet it is worth while to indicate briefly 

 both the methods and principles of classification, and the prac- 

 tical uses of careful description and naming. The material in 

 the text, it must be clearly understood, is not something to 

 be learned, but a convenient scheme of reference. Every plant 

 or animal that comes to the attention of the class should be 

 placed within its phylum, or class, or order, as conditions per- 

 mit; but no attempt should be made to get the pupils to 

 memorize the definitions of the various groupings. With fre- 

 quent reference to the scheme, however, it is certain that most 

 children will get all they need of taxonomy. 



There are no separate chapters on the chemical processes 

 often presented in elementary studies as fundamental to phys- 



