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All impressions are  classified as arches, loops, whorls and  composites.    In arches
the ridges run from one side to the other without marking any backward turn.    The

ridges may converge together and by
an upward thrust in the middle look
like a tent, when the arches are known
as "tented". In loop, whorl and com-
posite types there are fixed points,
which are known as the delta or outer
terminus and the point of the core or
inner terminus. These serve a useful
purpose in the classification of finger
impressions. The delta, may be formed
by the bifurcation of a single ridge or
by the abrupt divergence of two ridges
running side by side. The core of the
loop may consist either of an even or
uneven number of ridges, termed rods,

Fig. 12.—Rolled and plain impressions
of the left thumb.

not joined together or of two ridges
joined together at their summit, termed
staple. Some of the ridges exhibit a
backward turn without any twist. The
ridges round about the core frequently deviate in course from the general course of
the other ridges and leave a space which is described as a pocket and the loop
is then known as a pocket loop. Again, loops are described as twinned, when
a well-defined loop rests upon or surrounds another of the same variety. In
circular or elliptical whorls, the centre of the first ring is the point of the core. In
spiral whorls the point from which the spiral begins to revolve is the point of the core.
In composite types, arches, loops and whorls are grouped together in the same impres-
sion. They also include a small number of irregular patterns which cannot be classified
under any known variety of loops. For want of a better designation they are known as
accidentals. The finger impression printed on a paper is a reversal of the pattern on
the finger. For instance, if the pattern on the finger is a loop with slope from right to
left, it will appear in the print as a loop with slope from left to right. A loop is called
radial when the downward slope of the ridges about the core is from the direction of
the little finger towards that of the thumb. A loop is ulnar, when the downward slope is
from the direction of the thumb towards the little finger. About 5 per cent of impres-
sions are arches, 60 per cent loops and 35 per cent whorls and composites. The propor-
tion varies in several digits, but loops and whorls always predominate. For the purposes
of primary classification for criminal work arches are included under loops and compo-
sites under whorls. All the ten fingers are taken in the following pairs: —

left thumb

Right index           right ring finger

--------------->          ----------------------->     --------------------»

Right thumb          right middle ringer      right little finger

left middle
left index

left little

----------• >

left ring

When a whorl occurs in the first pair it counts 16 ; in the second pair 8 ; in the
third 4 ; in the fourth 2 ; and in the fifth 1. No value is fixed for loops. Obtain a new
numerator and a denominator by adding together all the numerators and all the deno-
minators. Add 1 to the numerator and also to the denominator thus obtained. The fraction
now obtained is the classification number and indicates that the _ slip is to be placed in
the pigeon-hole bearing that number.

Primary classification numbers

1 to

1,024 pigeon holes.    The  formula  for  the

W    L    L   W   W47

classification of these digits may be represented as -£»  ^ j> ^» -^— •

The system was first used by Sir William Herschel, I.C.S., but the credit
is given to Sir Francis Galton for having systematized it for the identification
of criminals. The system is so perfect that it has now been adopted all over
the civilized world. It may be noted that this science of finger prints was
known in ancient Assyria, and was used for purposes of identification in 700
A.D. The Chinese police were using it in the thirteenth century.48 In 1899,
an Act was passed by the Indian Council that the evidence given by experts

47.   For detailed description see Finger Print Manual, U.P., 1925 Reprint

48.   R. Scheffer, Zeutzalbltt Gynakologie, Leipzig, 50, Oct. 2, 1926, p. 2,559; Jourwd
Amer. Med. Assoc., Jan. 15, 1927, p. 214,