Prof. Ferner, of King's college, London, who luis made tlie phenomana of sleep a special study, recently said in a locture thereon that anythin'g whicli luis a teudeucy to abstract blood lroin the brain favors leep. Exerciso doos this, because the moment tbo weary muscles are at rest the blood rushes to them to repair their loss, and is absorbed by them. Digestión and hot drinks produce the same resul t by drawing the blood supply from the brain to the stomach. Oonversely, anythiug that stimulates the bruin, such as sightu, soumis, thought Of anxiety, will keep a man awake. If we, theroforo, wish for a refreshijjg slumbei', we must begin by avoidmg care andanxiety and take suiñoient bodily exeroise to induce thé necessary musculiu' rxliiiusiidii. Witli regard to the length of Kleej), J)r. Ferrier holde that the heart is oot is a state oí constant but oí rhythmical aotivity, o term of uction beiBg lollowed uya] ftuse of rest, during which the heart is to all intents and purposen asleep. In fact, if t!i( pauses of the heart are all summed mi, it will be found thnt it resta orsli eps eight hours out of the twenty-foiu, the sl;']) beiug in the propOTtion of oimthird as compared with ihe höurs of action or work. Kiglit liuurs are oonsrijueuüy sullioieut fol tho adult.