X PREFACE 



The sections in coarse type contain the material that seems 

 to the authors most essential for any clear understanding of 

 the subject as a whole, while in fine type we have put addi- 

 tional laboratory work and text description which we believe 

 to have an important bearing on the various topics discussed. 

 If both coarse and fine print on animal, or plant, or human 

 biology are used, sufficient material for a half-year course in 

 either elementary botany, zoology, or human physiology will 

 be provided. 



In the judgment of the authors, plant biology should always 

 be considered first and human biology last in the course for 

 the following reasons : (1) Plants lend themselves far more 

 readily to close observation and especially to experiments 

 than do .animals, and so fundamental processes which apply 

 to all living things can be demonstrated scientifically from 

 plant material. (2) Plants are the final source of all the food 

 supply of animals and man, and if the composition and manu- 

 facture of the nutrients are taught early in the course, a solid 

 foundation is laid for all subsequent study of nutrition in 

 animals and man. (3) The purpose of the animal study is 

 largely that of showing the adaptations of animal structure 

 to functions and the relations of the animals studied to 

 human welfare. (4) And finally, if human biology comes 

 last in the course, it may be presented in such a way as to 

 review, sum up, and give real significance to many of the 

 facts learned earlier in the course. In fact, as the work 

 proceeds, comparisons will constantly be made between 

 plants, animals, and man to show that the essential differ- 

 ences in the three kinds of organisms consist not in the dif- 

 ferences in the functions which they carry on, but in the 

 organs by which the functions are performed. 



So far as the order of individual topics under plant, ani- 

 mal, and human biology is concerned, the instructor should 



