The use of fingerprints for identification purposes is based upon distinctive ridge outlines which appear on the bulbs on the inside of the end joints of the fingers and thumbs. These ridges have definite contours and appear in several general pattern types, each with general and specific variations of the pattern, dependent on the shape and relationship of the ridges. The outlines of the ridges appear most clearly when inked impressions are taken upon paper, so that the ridges are black against a white background. This result is achieved by the ink adhering to the friction ridges. Impressions may be made with blood, dirt, grease or any other foreign matter present on the ridges, or the saline substance emitted by the glands through the ducts or pores which constitute their outlets. The background or medium may be paper, glass, porcelain, wood, cloth, wax, putty, silverware, or any smooth, nonporous material. Of all the methods of identification, fingerprinting alone has proved to be both infallible and feasible. Its superiority over the older methods, such as branding, tattooing, distinctive clothing, photography, and body measurements (Bertillon system), has been demonstrated time after time. While many cases of mistaken identification have occurred through the use of these older systems, to date the fingerprints of no two individuals have been found to be identical. The background and history of the science of fingerprints constitute an eloquent drama of human lives, of good and of evil. Nothing, I think, has played a part more exciting than that enacted by the fascinating loops, whorls, and arches etched on the fingers of a human being. [Signature: J. Edgar Hoover] J. EDGAR HOOVER, _Director._ _CONTENTS_ _Chapter_ _Page_ I. The Identification Division of the FBI 1 II. Types of Patterns and Their Interpretation 5 III. Questionable Patterns 71 IV. The Classification Formula and Extensions 87 V. Classification of Scarred Patterns--Amputation--Missing at Birth 98 VI. Filing Sequence 103 VII. Searching and Referencing 109 VIII. How To Take Inked Fingerprints 114 IX. Problems in the Taking of Inked Fingerprints 118 X. Problems and Practices in Fingerprinting the Dead 131 XI. Establishment of a Local Fingerprint Identification Bureau 160 XII. Latent Impressions 173 XIII. Powdering and Lifting Latent Impressions 175 XIV. Chemical Development of Latent Impressions 177 XV. The Use of the Fingerprint Camera 184