Abstract: A first syringe pump feeds a sample solution such as, for example, a diluted blood into an inner tube of a flow cell, and a second syringe pump feeds a sheath solution such as, for example, a physiological saline solution into an outer tube of the flow cell. Respective first and second plungers of the first and second syringe pumps are fixed onto a connecting plate. The connecting plate is supported by a pair of guide rods so that it may be moved in line with the moving direction of the plungers. Into the connecting plate is screwed an externally threaded rod, which is driven by a motor to rotate in the normal and reverse directions about its axis. By the normal and reverse rotations of the threaded rod, the connecting plate is reciprocally moved, whereby the first and second plungers are moved at the same speed. By the movement of the first and second plungers at the same speed, the sample solution and the sheath solution are respectively fed into the flow cell at the same rate.

Abstract: Described is a method of discriminating between front and back sides of the paper sheet bearing different printed design on the front and back sides, the printed design being in dissymmetry both in the up and down direction and in the left and right direction. The amount of light transmitted through plural portions of the paper sheet is sensed for deriving pattern signals indicative of changes in the amount of transmitted light, said pattern signals being then compared to reference pattern signals stored in advance to permit discrimination between the upper and lower edges and between the front and back sides of the sheet.