1. a system of classification based on the variations in the patterns of the ridges, which are grouped into arches, loops, and whorls (A.L.W. or arch-loop-whorl system). “Arches are formed when the ridges run from one side to the other of the bulb of the digit, without making any backward turn, but no twist; whorls, when there is a turn through at least one complete circle; they are also considered to include all duplex spirals.” The abbreviations used in making a record of fingerprints are: a, arch; l, loop; w, whorl; i, loop with an inner (thumb side) slope; o, loop with an outer (little-finger side) slope. The ten digits are registered in four groups as follows, distinguished by capital letters: A, the fore, middle, and ring fingers of the right hand; B, the fore, middle, and ring fingers of the left hand; C, the thumb and little finger of the right hand; D, the thumb and little finger of the left hand.
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