The Science of Fingerprints | Page 9

the line crosses an island, both sides are
counted. Fragments and dots are counted as ridges only if they appear
to be as thick and heavy as the other ridges in the immediate pattern.
Variations in inking and pressure must, of course, be considered.
Figures 72 to 97 and figures 98 to 101 show various loop patterns. The
reader should examine each one carefully in order to study the cores
and deltas and to verify the count which has been placed below each
pattern.

[Illustration: 72. 12 counts.]
[Illustration: 73. 2 counts.]
[Illustration: 74. 16 counts.]
[Illustration: 75. 7 counts.]
[Illustration: 76. 4 counts.]
[Illustration: 77. 7 counts.]
[Illustration: 78. 15 counts.]
[Illustration: 79. 16 counts.]
[Illustration: 80. 9 counts.]
[Illustration: 81. 3 counts.]
[Illustration: 82. 9 counts.]
[Illustration: 83. 20 counts.]
[Illustration: 84. 6 counts.]
[Illustration: 85. 2 counts.]
[Illustration: 86. 8 counts.]
[Illustration: 87. 14 counts.]
[Illustration: 88. 5 counts.]
[Illustration: 89. 12 counts.]
[Illustration: 90. 12 counts.]
[Illustration: 91. 3 counts.]

[Illustration: 92. 16 counts.]
[Illustration: 93. 14 counts.]
[Illustration: 94. 16 counts.]
[Illustration: 95. 18 counts.]
[Illustration: 96. 2 counts.]
[Illustration: 97. 1 count.]
[Illustration: 98. 1 count.]
[Illustration: 99. 2 counts.]
[Illustration: 100. 8 counts.]
[Illustration: 101. 13 counts.]
Figure 102 is a sketch reflecting the various types of ridges which the
classifier will encounter when engaging in counting loop patterns.
In figure 103, the lighter lines are caused by the splitting or fraying of
the ridges. Sometimes ingrained dirt will cause a similar condition
between the ridges. These lines are not considered ridges and should
not be counted.
In figure 104, the dot is not the delta because it is not as thick and
heavy as the other ridges and might not be present if the finger were not
perfectly inked and printed.
When the core is located on a spike which touches the inside of the
innermost recurving ridge, the recurve is included in the ridge count
only when the delta is located below a line drawn at right angles to the
spike.
Figures 105 and 106 are examples of this rule.

If the delta is located in areas A, the recurving ridge is counted.
If the delta is located in areas B, the recurving ridge is not counted.
[Illustration: 102]
LOOP 25 RIDGE COUNTS
1. SHORT RIDGE 2. } 3. } BIFURCATION 4. } 5. } BIFURCATION
6. RIDGE 7. ENDING RIDGE 8. } 9. } BIFURCATION 10. RIDGE
11. ENDING RIDGE 12. RIDGE 13. SHORT RIDGE 14. } 15. }
BIFURCATION 16. } 17. } ISLAND 18. } 19. } BIFURCATION 20.
ENDING RIDGE 21. DOT 22. RIDGE 23. } 24. } ISLAND 25.
ENDING RIDGE
[Illustration: 103]
[Illustration: 104]
[Illustration: 105]
[Illustration: 106]
Radial and ulnar loops
The terms "radial" and "ulnar" are derived from the radius and ulna
bones of the forearm. Loops which flow in the direction of the ulna
bone (toward the little finger) are called ulnar loops and those which
flow in the direction of the radius bone are called radial loops.
For test purposes, fingers of the right hand may be placed on the
corresponding print of the right hand appearing in figure 71, and it will
be noticed that the side of each finger which is nearer to the thumb on
the hand is also nearer to the thumb on the fingerprint card. Place the
fingers of the left hand on the corresponding prints of the left hand
shown in figure 71. It will be noticed that the arrangement of the prints
on the card is the reverse of the arrangement of the fingers on the hand.
The classification of loops is based on the way the loops flow on the
hand (not the card), so that on the fingerprint card for the left hand,

loops flowing toward the thumb impression are ulnar, and loops
flowing toward the little finger impression are radial.
The plain arch
In plain arches the ridges enter on one side of the impression and flow
or tend to flow out the other with a rise or wave in the center. The plain
arch is the most simple of all fingerprint patterns, and it is easily
distinguished. Figures 107 to 118 are examples of the plain arch. It will
be noted that there may be various ridge formations such as ending
ridges, bifurcations, dots and islands involved in this type of pattern,
but they all tend to follow the general ridge contour; i.e., they enter on
one side, make a rise or wave in the center, and flow or tend to flow out
the other side.
[Illustration: 107]
[Illustration: 108]
[Illustration: 109]
[Illustration: 110]
Figures 119 and 120 are examples of plain arches which approximate
tented arches. Also, figure 121 is a plain arch approximating a tented
arch as the rising ridge cannot be