Europe in accordance with physiological principles, so as to illustrate the orderly progress of civilization, or collected the facts furnished by other branches of science with a view of enabling us to recognize clearly the conditions under which that progress takes place. This philosophical deficiency I have endeavoured in the following pages to supply.
Seen thus through the medium of physiology, history presents a new aspect to us. We gain a more just and thorough appreciation of the thoughts and motives of men in successive ages of the world.
In the Preface to the second edition of my 'Physiology,' published in 1858, it was mentioned that this Work was at that time written. The changes that have been since made in it have been chiefly with a view of condensing it. The discussion of several scientific questions, such as that of the origin of species, which have recently attracted public attention so strongly, has, however, remained untouched, the principles offered being the same as presented in the former work in 1856.