PREFACE 



The subject matter falls naturally into three parts. The 

 first part is general in character. It contains reflections 

 upon the philosophy of biology and upon the validity of 

 its conclusions. Here the authors have also tried to show 

 how the field of biology is ever broadening through the 

 inclusion of problems which were formerly thought to be 

 beyond the reach of scientific procedure. The second part 

 is concerned with the mind. It contains a skeletonized 

 account of the general development of psychology, and 

 essays on the application of psychological methods to 

 education and to industry. The third part treats of the body. 

 It is designed to show, in some measure, the progress in 

 dealing with man as an animal. It portrays some of the 

 advances in genetics, in medicine, in the work of the 

 public health officer, in physiology, in biochemistry, and 

 in general zoology put to the service. In addition, there is 

 an extended discussion of the means by which man increases 

 his food supply and thus makes it possible to feed some 

 twenty million additional people with the advent of each 

 new season. 



E. M. E. 



Boston, Massachusetts, 

 February, 1931. 



[ix] 



