PREFACE TO THE REVISED EDITION. vii 



I have every reason to believe that our course of in- 

 struction in Elementary Biology has been found useful by 

 many learners and teachers. But whatever the value of 

 our attempt to carry out a certain method of instruction, I 

 am more than ever convinced that the method itself is one 

 which will eventually be universally adopted, not only by 

 teachers of the biological sciences as such, but by the 

 teachers of so much of those sciences as constitute the 

 foundation of medicine. 



No man can be competent to deal with the greater 

 problems of biology as they are now presented to us, unless 

 he has made a survey, at once comprehensive and thorough, 

 of the whole field of biological investigation. The animal 

 and the vegetable worlds are only two aspects of the same 

 fundamental series of phenomena, and each is capable of 

 throwing a flood of light upon the other. I know of no 

 way by which such a broad, but not superficial, survey can 

 be effected except the method adopted in this work. 



Again, while to my mind, nothing is more to be 

 deprecated than the compulsory waste of the invaluable 

 time of students of medicine, upon topics so remote from 

 the serious business of their lives as are systematic Zoology 

 and Botany, there is no preparatory discipline so well 

 calculated to serve as a practical introduction to the study 

 of Human Anatomy and Physiology, as that afforded by a 

 proper laboratory course of Elementary Biology. 



Sundry experiments have left no doubt upon my mind 

 that, by following such a course of three or four months' 

 duration, the medical neophyte is enabled to enter upon 

 his proper studies, provided with a practical knowledge of 



