n interval would intervene as in figures 53 and 54.

[Illustration: 53]

[Illustration: 54]

[Illustration: 55]

_The loop_

In fingerprints, as well as in the usual application of the word
"loop," there cannot be a loop unless there is a recurve or turning
back on itself of one or more of the ridges. Other conditions have to
be considered, however. A pattern must possess several requisites
before it may be properly classified as a loop. This type of pattern
is the most numerous of all and constitutes about 65 percent of all
prints.

_A loop is that type of fingerprint pattern in which one or more of
the ridges enter on either side of the impression, recurve, touch or
pass an imaginary line drawn from the delta to the core, and terminate
or tend to terminate on or toward the same side of the impression from
whence such ridge or ridges entered._

_Essentials of a loop_

- A sufficient recurve.

- A delta.

- A ridge count across a looping ridge.

_A sufficient recurve may be defined as that part of a recurving ridge
between the shoulders of a loop. It must be free of any appendages
abutting upon the outside of the recurve at a right angle._

_Appendages_--Some explanation is necessary of the importance attached
to appendages. Much care must be exercised in interpreting appendages
because they sometimes change the shape of the recurving ridge to
which they are connected. For example, a loop with an appendage
abutting upon its recurve between the shoulders and at right angles,
as in illustration 56, will appear sometimes as in illustration 57
with the recurve totally destroyed. For further examples see figures
161 to 184.

[Illustration: 56]

[Illustration: 57]

The same is true of a whorl recurve, as in figures 58 and 59.

It is necessary, therefore, to consider and classify figures 56 and 58
as if they actually appeared as in figures 57 and 59.

In figure 60, there is a ridge marked "A" which enters on one side of
the impression and, after recurving, passes an imaginary line drawn
from the core C to delta D, and terminates on the same side of the
impression from which it entered, marked "B", thus fulfilling all the
conditions required in the definition of a loop. X and Y are the type
lines. It will be noted in figure 61 that there is a ridge which
enters on one side of the impression, recurves, and passes an
imaginary line drawn from the delta to the core. It does not terminate