4 PREFACE 



the actual connection of every vital process with the one nervous 

 system becomes obvious, and the emphasis is placed where it properly 

 belongs. It is believed that this plan has advantages also for the 

 student of general biology. It emphasizes the one grand, obvious 

 distinction between plants and animals. To students of psychology 

 it will likewise commend itself. Because of prevalent ignorance of 

 the nervous system and its due predominance in the animal economy, 

 psychologists have been forced to become physiologists in order to 

 build across the gap, left by the ordinary manner of treatment, 

 between physiology and psychology. 



Care has been taken to make no statements not in accord with 

 established science, but no effort is made to introduce the newest 

 conjectures. The necessary limitations of a school text-book have 

 been kept in mind as well as the degree of mental development of 

 those for whom the work is designed. 



It is believed that the instruction respecting alcoholic drinks and 

 narcotics, while complying with the requirements of recent legislation 

 in the various states, will be found to be based upon rational and 

 scientific principles, and to be placed before the student in a manner 

 to win the assent of his reason rather than to create a mere prejudice 

 which further knowledge might overthrow. Nothing is gained by 

 overstatement, and it is always safe to tell the simple truth, for 

 nothing will so surely foster right living as a knowledge of the truth. 



The writer has had much assistance from experienced and compe- 

 tent teachers and physicians. Dr. A. W. Alvord (M.D., University 

 of Michigan) of Battle Creek, Michigan, has kindly revised the 

 hygienic portions of the book. Mr. H. W. Norris, A. M., Professor of 

 Biology in Iowa College, has read and criticised the whole of the 

 manuscript. All of the experimental work has been prepared by him 

 and will be found of especial value. Many of the illustrations used 

 are such as are commonly found in schoolbooks treating the subject 

 of physiology, but a large number have been adapted from cuts in 

 recent advanced works, mainly those by Morris, Spalteholz, and Van 

 Gehuchten ; while numerous other drawings expressly for this work 

 have been made by Mr. E. W. Atherton under the direction of 

 Professor Norris. 



