It does not follow that because men will some day have this enormous power over themselves, physically and mentally, that they will necessarily make themselves horrible—­even by our present standards quite a lot of us would be all the slenderer and more active and graceful for “Metchnikoffing”—­nor does surgery exhaust the available methods.  We are still in the barbaric age, so far as our use of food and drugs is concerned.  We stuff all sorts of substances into our unfortunate interiors and blunder upon the most various consequences.  Few people of three score and ten but have spent in the aggregate the best part of a year in a state of indigestion, stupid, angry or painful indigestion as the case may be.  No one would be so careless and ignorant about the fuel he burnt in his motor-car as most of us are about the fuel we burn in our bodies.  And there are all sort of stimulating and exhilarating things, digesting things, fatigue-suppressing things, exercise economising things, we dare not use because we are afraid of our ignorance of their precise working.  There seems no reason to suppose that human life, properly understood and controlled, could not be a constant succession of delightful and for the most part active bodily and mental phases.  It is sheer ignorance and bad management that keep the majority of people in that disagreeable system of states which we indicate by saying we are “a bit off colour” or a little “out of training.”  It may seem madly Utopian now to suggest that practically everyone in the community might be clean, beautiful, incessantly active, “fit,” and long-lived, with the marks of all the surgery they have undergone quite healed and hidden, but not more madly Utopian than it would have seemed to King Alfred the Great if one had said that practically everyone in this country, down to the very swineherds, should be able to read and write.

Metchnikoff has speculated upon the possibility of delaying old age, and I do not see why his method should not be applied to the diurnal need of sleep.  No vital process seems to be absolutely fated in itself; it is a thing conditioned and capable of modification.  If Metchnikoff is right—­and to a certain extent he must be right—­the decay of age is due to changing organic processes that may be checked and delayed and modified by suitable food and regimen.  He holds out hope of a new phase in the human cycle, after the phase of struggle and passion, a phase of serene intellectual activity, old age with all its experience and none of its infirmities.  Still more are fatigue and the need for repose dependent upon chemical changes in the body.  It would seem we are unable to maintain exertion, partly through the exhaustion of our tissues, but far more by the loading of our blood with fatigue products—­a recuperative interlude must ensue.  But there is no reason to suppose that the usual food of to-day is the most rapidly assimilable nurture possible, that a rapidly digestible or injectable substance is