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Rh exudes. Then gently, with finger and thumb, squeeze the finger-pad and express a second minute droplet of blood; this should be very small—no larger than a pin's head. Touch the droplet lightly with the centre of a cover-glass, taking care that the latter does not come into contact with the skin, and immediately drop the cover-glass on the slide. No pressure should be used to cause the blood to spread out. If glasses and skin are quite clean, the blood will at once run out in a



Several preparations should be made, the requisite blood being obtained by renewed gentle compression of the finger-tip.

After waiting a few minutes to allow the blood to spread out completely between the glasses, it is well to ring the preparations with vaseline. This will effectually stop all movement, all evaporation of