In three other points their physiology differed strangely from
ours.  Their organisms did not sleep, any more than the heart of man
sleeps.  Since they had no extensive muscular mechanism to recuperate,
that periodical extinction was unknown to them.  They had little or
no sense of fatigue, it would seem.  On earth they could never have
moved without effort, yet even to the last they kept in action.  In
twenty-four hours they did twenty-four hours of work, as even on earth
is perhaps the case with the ants.