required to recuperate from the long vigil. They were allowed to sleep
themselves out, and all woke up thoroughly rested. _Yet the one who
slept the longest slept only one-third longer than his customary
night's sleep._

You have doubtless had the same experience yourself many times. It all
goes to show that if we are awake four times as long as usual, we do
not make up for it by sleeping four times as _long_, but four times as
_soundly_, as customary. The hard-working mechanic requires no more
hours of sleep than the corner loafer, the active man of affairs no
more than the dawdler.

[Sidenote: _Ratio Between Repair and Demand_]

_The time of tissue repair is about the same with all men under all
conditions. It is the rate of repair that varies with the demand that
has been put upon the body._

Again, look at the same subject from the standpoint of food supply. On
what you now eat and drink you have a certain average weight. Eat,
digest and assimilate a larger quantity of food and your weight will
increase. This increase will be greatest at the start and will
gradually slow up until you shall have reached the point beyond which
you can gain no more. Given the same hygienic conditions that you have
been accustomed to, you will maintain yourself at the increased weight
on the increased supply of food.

[Sidenote: _Pygmies and Giants_]

Now, all this involves clearly enough a greatly increased rate of