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 considered an upthrust because it is a continuous, and not an ending, ridge. (See following explanation of the tented arch.) [Illustration: 111] [Illustration: 112] [Illustration: 113] [Illustration: 114] [Illustration: 115] [Illustration: 116] [Illustration: 117] [Illustration: 118] [Illustration: 119] [Illustration: 120] [Illustration: 121] _The tented arch_