It is hardly a “burning question”; it is not even a “problem that
presses for solution.” Nevertheless, to minds not incurious as to the
future it has a mild, pleasing interest, like that of the faintly heard
beating of the bells of distant cows that will come in and demand
attention later.
It by no means appears that sleep is a natural function, the necessity
of which inheres in animal life and the constitution of things;
there is reason to regard it as a phenomenon due rather to stress of
circumstances—a kind of intermittent disorder incurred by exposure
to conditions that are being slowly but surely removed. Precisely
as sanitary and medical science and improved methods of living are
gradually extending the length of human life in every civilized country
and threatening the king of shadows himself with death ere, in the
poet’s sense, “Time shall throw a dart” at him, so we may observe
already the initial stages of a successful campaign against his brother
“Sleep.” Civilized peoples sleep fewer hours than savage ones, and,
among the civilized, dwellers in cities fewer than country folk. The
reason is not far to seek: it is a matter of light.
Primitive Man, like the savage of to-day, had at night no other light
than that of the moon and that of wood fires. For countless ages our
ancestors lived without candles, and when they had learned the trick
of burning rushes soaked in the fat of neighboring tribesmen their
state was not greatly better. Beyond Primitive Man we may dimly discern
_his_ ancestors—unmentionable to ears un-Darwinized—who had no
artificial light at all. In the darkness of the night and the forest
what could these ancient worthies do? They had little enough to do at
any time, but even their rudest pursuit—that of one another—could not
be carried on in darkness. They did nothing, naturally assuming the
most comfortable posture in which to do it, the earlier sort suspending
themselves by their tails, the later, having no tails, lying down as
we do to-day, or rather to-night. It is a law of nature that when the
body, or any organ of it, is inactive a kind of torpor ensues; the
blood circulates in it with a more feeble flow; molecular changes take
place with a lessened energy—in short, the creature begins to die, and
can be restored to full life only by renewal of bodily activity. In the
instance of the brain this torpor means unconsciousness—that is to say,
sleep. To put the matter briefly, darkness compels inaction, inaction
begets sleep.
Another law of nature—a rather comical one—is that acts which we do
regularly, from choice or necessity, set up a tendency in us to do them
involuntarily when we don’t care to; and when the original impulse
has been replaced by this new and more imperative one we give it the
name of habit and flatter ourselves that we have explained it. Because
our pithecanthropoid and autocthonic forefathers, unable by reason of
darkness to indulge during the whole twenty-four hours in the one-sided
pleasures of the chase and the mutual joy of braining one another, had
to sleep, _we_ have to sleep; although we have (by paying sorely
for it) plenty of light for many kinds of malign activity.
But little by little we are overcoming the sleep habit without loss of
health, if not with positive sanitary advantage. As before pointed out,
the people of our lighted cities sleep less than the rural population;
and this sleeps less than it did before the improvement in lamps.
Nothing is more certain, despite popular opinion to the contrary,
than that the men of cities are superior in strength and endurance to
those of the country, as is abundantly attested in army life, in camp
and field. That this is wholly or even greatly due to their nocturnal
activity is not affirmed; only that their addiction to the joys of
insomnia has not appreciably counteracted the sanitary advantages of
city life—amongst which an honorable prominence should be given to
defective drainage and drinking-water that is largely solution of dog
and hydrate of husband from the city reservoir.
The electric light has apparently “come to stay,” but more likely it
will in good time be replaced by something that as far exceeds it as
itself beats the hallowed tallow candle of our grandmothers. Not only
will the streets and shops and dwellings of our cities be illuminated
all night with a splendor of which we can have hardly a conception,
but the country districts as well; for it is now known that plants
(which apparently are not creatures of habit) do not need sleep, and
that by continuous light the profits of agriculture could be enormously
increased. The farmers will no longer retire with the lark, but will
work night shifts, as is already done in factories and mines, and
eventually work all the time, in order to support the rest of us in the
style to which we have been accustomed.
On the whole, I think it not unreasonable to look forward with
pleasant anticipation to a time, some millions of years hence, when
the literature of sleep will be no longer intelligible, and the people
of even this country be sufficiently wide awake to prevent the ten
_per centum_ of their number devoted to patriotic pursuits from
plundering the other ninety _per centum_, and to make our judges
and legislators obey the laws.