Mereisanastonishingandsignificantfact:Mentalworkalonecan’tmakeustired.Itsoundsabsurd.Butafewyearsagoscientiststriedtofindouthowlongthehumanbraincouldlaborwithoutreachingastageoffatigue(疲劳).Totheamazementofthesescientiststheydiscoveredthatbloodpassingthroughthebrainwhenitisactive，showsnofatigueatall!Ifwetookadropofbloodfromadaylaborerwewouldfinditfulloffatiguetoxins(毒素）andfatigueproducts.ButifwetookbloodfromthebrainofanAlbertEinsteinitwouldshownofatiguetoxinsattheendoftheday.
Sofarasthebrainisconcerneditcanworkaswellandswiftlyattheendofeightoreventwelvehoursofeffortasatthebeginning.Thebrainistotallytireless.Sowhatmakesustired?
Somescientistsdeclarethatmostofourfatiguecomesfromourmentalandemotional(情感的）attitudes.OneofEngland’smostoutstandingscientistsJ.A.Hadfield，says“Thegreaterpartofthefatiguefromwhichwesufferisofmentalorigin.Infactfatigueofpurelyphysicaloriginisrare.”Dr.BrillafamousAmericanscientistgoesevenfurther.Hedeclares“Onehundredpercentofthefatigueofasittingworkeringoodhealthisduetoemotionalproblems.”
Whatkindsofemotionsmakesittingworkerstired?Joy?Satisfaction?No!Afeelingofbeingbored，angeranxietytensenessworryafeelingofnotbeingappreciated-thosearetheemotionsthattiresittingworkers.Hardworkbyitselfseldomcausesfatigue.Wegettiredbecauseouremotionsproducenervousnessinthebody.
64.Whatsurprisedthescientistsafewyearsago?
A. Fatiguetoxinscouldhardlybefoundinalaborer’sblood.
B. AlbertEinsteindidn’tfeelwornoutafteraday’swork.
C. Thebraincouldworkformanyhourswithoutfatigue.
D. Amentalworker’sbloodwasfilledwithfatiguetoxins.
65.Accordingtotheauthorwhichofthefollowingcanmakesittingworkerstired?
A. Challengingmentalwork.
B. Unpleasantemotions.
C. Endlesstasks.
D. Physicallabor.
66.What'stheauthor’sattitudetowardsthescientists’ideas?
A. Heagreeswiththem.
B. Hedoubtsthem.
