PREFACE ix 



century, hypnotism, or mesmerism as it was then 

 called, was in complete scientific disrepute. To-day, 

 all the main claims of its founders have been verified, 

 and many new facts unearthed. Every text-book 

 on the subject will tell you that men may be made 

 insensible to pain by hypnosis alone without any 

 drug, many women even being delivered of children 

 under its influence without suffering. Temperature 

 can be changed, blisters raised, and many other proc- 

 esses not normally under the control of the will can 

 similarly be affected. The mind can be raised to an 

 abnormal sensitiveness, in which differences between 

 objects that are completely unrecognizable in ordi- 

 nary waking existence, such as those between the 

 backs of two cards in a pack, may be easily distin- 

 guished. 



If such possibilities are open to the empiricism of 

 the hypnotist, what may we not await from any truly 

 scientific knowledge of mind, comparable even in low 

 degree to our knowledge of, say, electricity? 



But these in a sense are all details, relevant in a 

 way, and yet only details. There is something still 

 more fundamental in the biologist's attitude. He 

 has to study evolution, and in that study there is 

 brought home to him, more vividly than to any one 

 to whom the facts are not so familiar, that in spite of 

 all appearances to the contrary there has been, 

 throughout the whole of evolution, and most 

 markedly in the rise of man from his pre-human for- 

 bears, a real advance, a progress. 



