each of outside influences as if they were governed by clockwork. The
_animal_ functions, as the physiologists call them, in distinction from
the _organic_, tend, in the process of deterioration to which age
and neglect united gradually lead them, to assume the periodical or
rhythmical type of movement. Every man's _heart_ (this organ belongs,
you know, to the organic system) has a regular mode of action; but I
know a great many men whose _brains_, and all their voluntary existence
flowing from their brains, have a _systole_ and _diastole_ as regular
as that of the heart itself. Habit is the approximation of the animal
system to the organic. It is a confession of failure in the highest
function of being, which involves a perpetual self-determination, in
full view of all existing circumstances. But habit, you see, is an
action in present circumstances from past motives. It is substituting a
_vis a tergo_ for the evolution of living force.

When a man, instead of burning up three hundred pounds of carbon a
year, has got down to two hundred and fifty, it is plain enough he must
economize force somewhere. Now habit is a labor-saving invention which
enables a man to get along with less fuel,--that is all; for fuel is
force, you know, just as much in the page I am writing for you as in the
locomotive or the legs that carry it to you. Carbon is the same thing,
whether you call it wood, or coal, or bread and cheese. A reverend
gentleman demurred to this statement,--as if, because combustion is
asserted to be the _sine qua non_ of thought, therefore thought is
alleged to be a purely chemical process. Facts of chemistry are one
thing, I told him, and facts of consciousness another. It can be proved
to him, by a very simple analysis of some of his spare elements,
that every Sunday, when he does his duty faithfully, he uses up more
phosphorus out of his brain and nerves than on ordinary days. But then
he had his choice whether to do his duty, or to neglect it, and save his
phosphorus and other combustibles.

It follows from all this that _the formation of habits_ ought naturally
to be, as it is, the special characteristic of age. As for the muscular
powers, they pass their maximum long before the time when the true
decline of life begins, if we may judge by the experience of the ring. A
man is "stale," I think, in their language, soon after thirty,--often,
no doubt, much earlier, as gentlemen of the pugilistic profession are
excee