THE PLAN AND PURPOSE OF THIS BOOK 



The plan of this book recognizes first-year biology as a science 

 founded upon certain underlying and basic principles. These prin- 

 ciples underlie not only biology, but also organized society. The 

 culmination of such an elementary course is avowedly the under- 

 standing of man, and the principles which hold together such a 

 course should be chiefly physiological. The functions of all living 

 things, plant or animal, movement, irritability, nutrition, respira- 

 tion, excretion, and reproduction ; the interrelation of plants and 

 animals and their economic relations, all these as they relate to 

 man should enter into a course in elementary biology. 



But to make plain these physiological processes, difficult even 

 for an advanced student of biology to comprehend, the simplest 

 method of demonstration is necessary. Plant physiology, because 

 of the ease with which simple demonstrations can be made, is 

 more profitable ground for beginners than is the physiology of 

 animals. The foods which animals use are manufactured and 

 used by green plants; the action of the digestive enzymes, the 

 principle of osmosis, and the subject of reproduction can better 

 be first handled from the botanical aspect. The topics just men- 

 tioned introduced from the standpoint of the botanist gain much 

 by repetition from the zoological angle. The principles of physi- 

 ology, after being apphed in experiment to plants and animals, 

 emerge in final clarity when apphed at the last to man, — the 

 most complex of all living things. 



One of the most important factors in successful science teaching 

 is repetition. In a recent address President Remsen of Johns 

 Hopkins University said : — 



" The most important defect in the teaching of chemistry to-day is the 

 absence of repetition. There are too many fleeting impressions. We cover 

 too much ground. The student gets only a veneer." 



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