{HEAD ~ A laser beam} is focussed on to a capillary by {TAIL ~ means} of a lens, mirror and beam splitter system and measurement of the velocity of the blood cells in a direction substantially perpendicular to the surface of the tissue is effected by detecting directly back scattered radiation 
{ HEAD ~ A laser beam } is focussed on to a capillary by { TAIL ~ means } of a lens , mirror and beam splitter system and measurement of the velocity of the blood cells in a direction substantially perpendicular to the surface of the tissue is effected by detecting directly back scattered radiation
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