SLEEPERS, in natural history, a name given to those animals which sleep all winter; such as bears, marmots, dormice, bats, hedge-hogs, swallows, &c. These do not feed in winter, have no sensible evacuations, breathe little or none at all, and most of the viscera cease from their functions. Some of these creatures seem to be dead, and others return to a state like that of the fetus before birth: in this state they continue, till by length of time maturing the process, or by new heat the fluids are attenuated, and the functions begin where they left off.