VI PREFACE 



The book is written for two groups of readers. First, for 

 students who are about to specialize and can do so more 

 intelligently after they have seen in perspective what lies 

 ahead. This appHes particularly to medical students who 

 in order to be good physicians must above all be good 

 biologists. A knowledge of what is known of human hfe 

 past, present and possible future, is for them essential. In 

 the second place it is hoped that the book will be of interest 

 to readers of mature years occupied both in science and in 

 business who have an inquiring turn of mind and wish to 

 look a little below the surface. In this way it may assist in 

 the movement in favor of "adult education" which is 

 gaining momentum within the United States and is destined 

 to spread. 



Valuable suggestions have been received from many 

 quarters not only by the Editor, but by the individual 

 contributors who have one and all entered enthusiastically 

 into the spirit of the enterprise writing on their own re- 

 sponsibility and making acknowledgment when necessary. 

 The editor, however, is particularly grateful to Dr. Conklin, 

 Mr. Embree, Dr. Gregory and Mr. Hoeber for their con- 

 tinued interest and advice. 



E. V. COWDRY. 



Washington University, 



St. Louis, 



January 2,1930. 



