PREFACE 



THE investigations recorded in this volume, begun 

 nearly fifteen years ago, were inaugurated in consequence 

 of certain fundamental ideas or theories held by the writer, 

 and these have directed and dominated all our labors along 

 this line. The purpose of this work has been to solve 

 scientific problems, rather than to discover practical 

 applications. The latter, so far as they have in any way 

 influenced our studies or even received our attention, have 

 been only incidental. Quite naturally our theories have 

 been more or less modified, and have developed as the work 

 has progressed, but the essentials and fundamentals have 

 not been materially altered. From time to time these 

 theories have been given in more or less detail, notably 

 in an address at the opening of the Medical Department of 

 the University of Toronto in 1905 (Canadian Jour, of 

 Med. and Surg., xviii, 283) and in the Shattuck lecture for 

 1906 (Boston Med. and Surg. Jour., civ, 215). However, 

 it may be well to restate briefly the original conceptions 

 which impelled us to begin and continue these studies. 



The only essential and constant difference between 

 living and non-living matter is that within the molecules 

 of the former there is constant metabolism, while in the 

 latter no such process operates. We are to conceive of 

 the living molecules as made up of numerous atoms, and 

 each atom surrounded by its electrons; atoms and elec- 



