on a fine particle increases in proportion to a square of the particle size and further this apparatus can compute a platelet aggregation rate as well as a size of the produced platelet aggregate and the number thereof in the conventional extinction method the absorbance was lowered only after the aggregates comprising thousands of platelets were produced however the apparatus of the present invention can measure even small aggregates composed of tens of platelets that is this apparatus is excellent in its detection sensitivity the platelet aggregate sizes were classified into three groups as follows depending on the scattered light intensities 25 mv lt a small aggregate particle size 9 to 25 u03bcm lt 200 mv 200 mv lt a medium aggregate particle size 25 to 50 u03bcm lt 600 mv and 600 mv lt a large aggregate particle size 50 to 70 u03bcm lt 2 047 mv hoshi k zhou x terazono m satou y yamazaki m miyake f jpn j clin pharmacol ther 32 223 230 2001 x scattering intensity or od obtained by adding adp or collagen after ingesting nattokinase y scattering intensity or od obtained by adding adp or collagen before ingesting nattokinase when 1 0 u03bcg ml of collagen was added as a coagulant a strong inhibitory.