VI PREFACE 



some appear to be too discursive, but I base my 

 defence on the complexity of the subject with 

 which I deal, and on the plea that it does 

 in effect touch upon such varying depart- 

 ments of science as chemistry, pathology, 

 physiology, and their practical branches. To 

 understand the theory that I here advance, 

 a recognition of the claim put forward by 

 Professor Thompson for a sympathetic and 

 unbiassed inquiry into the Order of Nature is 

 the first necessity. 



E. F. W. 



