▁h emat oc rit , ▁that ▁is , ▁the ▁volume ▁concentration ▁of ▁red ▁cells ▁in ▁the ▁whole ▁blood ▁by ▁red ist rib uting ▁water ▁between ▁the ▁int ra vas cular ▁and ▁extra vas cular ▁spaces . ▁This ▁in ▁turn ▁affect s ▁the ▁mechan ics ▁of ▁the ▁whole ▁blood . ▁ ▁Red ▁blood ▁cells ▁The ▁red ▁blood ▁cell ▁is ▁highly ▁flexible ▁and ▁b icon ca ve ▁in ▁shape . ▁Its ▁memb rane ▁has ▁a ▁Young ' s ▁mod ulus ▁in ▁the ▁region ▁of ▁ 1 0 6   Pa . ▁De formation ▁in ▁red ▁blood ▁cells ▁is ▁induced ▁by ▁she ar ▁stress . ▁When ▁a ▁susp ension ▁is ▁she ared , ▁the ▁red ▁blood ▁cells ▁de form ▁and ▁spin ▁because ▁of ▁the ▁velocity ▁gradient , ▁with ▁the ▁rate ▁of ▁de formation ▁and ▁spin ▁depending ▁on ▁the ▁she ar - rate ▁and ▁the ▁concentration . ▁This ▁can ▁influence ▁the ▁mechan ics ▁of ▁the ▁circul ation ▁and ▁may ▁comp licate ▁the ▁measurement ▁of ▁blood ▁vis cos ity . ▁It ▁is ▁true ▁that ▁in ▁a ▁steady ▁state ▁flow ▁of ▁a ▁vis c ous ▁fluid ▁through ▁a ▁rig id ▁spher ical ▁body ▁imm ers ed ▁in ▁the ▁fluid , ▁where ▁we ▁assume ▁the ▁in ert ia ▁is ▁neg lig ible ▁in ▁such ▁a ▁flow , ▁it ▁is ▁believed ▁that ▁the ▁down ward ▁gravit ational ▁force ▁of ▁the ▁particle ▁is ▁bal anced ▁by ▁the ▁vis c ous ▁drag ▁force . ▁From ▁this ▁force ▁balance ▁the ▁speed ▁of ▁fall ▁can ▁be ▁shown ▁to ▁be ▁given ▁by ▁Sto kes ' ▁law