Dr. Ferrier, in lecturing at the London Institution on Monday
on " Sleep," laid it down that neither any living being, nor any function of any living being, is capable of unintermitted activity. If any organ of the body seems to be in perpetual activity, that is only appearance. The heart sleeps as much as the muscles, but then the heart's sleep is rhythmical, taken in the interval between the diastole and systole, or, to put the same thing more familiarly, is taken in a great number of very short naps indeed, which amount, however, when added together, to eight hours out of the 24, or one-third of the whole day. If that be rest enough, we do not quite see why the same sort of rest might not do for the brain,—which, even as it is, in most men seems to work in frequently repeated leaps or impulses of concentration, interrupted by minute reveries or dreams of relaxed effort, rather than strictly continuously. And certainly, in sleep, the brain often seems to be, if not as hard-worked as ever, at least very hard at it, dreaming, as Carlyle says, "the foolishe,st dreams," but not the less elaborate and tasking for that. What an advantage any race of men would have whose brains, while equally developed with ours, should be sufficiently rested by the minute, but repeated, intervals of repose which seem to suffice for the heart !
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