It is believed that by following the basic ideas outlined, the officials of law enforcement agencies can be assured of best results in establishing and maintaining a small identification bureau. For further information, the Federal Bureau of Investigation will furnish to duly constituted law enforcement officials any additional data which may be of material assistance in the maintenance of such a bureau. CHAPTER XII _Latent Impressions_ Each ridge of the fingers, palms, and soles bears a row of sweat pores which in the average person constantly exude perspiration. Also, the ridges of the fingers and palms are in intermittent contact with other parts of the body, such as the hair and face, and with various objects, which may leave a film of grease or moisture on the ridges. In touching an object, the film of moisture and/or grease may be transferred to the object, thus leaving an outline of the ridges of the fingers or palm thereon. This print is called a latent impression, the word "latent" meaning hidden, that is, the print many times is not readily visible. Latent impressions, regardless of the area of the ridges present, are of the greatest importance to the criminal investigator as identification of them may solve the crime and result in successful prosecution of the subject. Consequently, every effort should be made to preserve and _identify_ them. Visible prints in mediums such as blood, grease, dirt, or dust are equally important to the investigator but, strictly speaking, are not latent impressions. A search of the crime scene should be conducted in a logical manner. Points of entry and exit should be examined, along with surfaces or objects disturbed or likely touched during the commission of the crime. The examiner should wear a pair of light cloth gloves and handle an object only insofar as is necessary and then only by edges or surfaces which are not receptive to latent impressions. A record of the exact location of a print on an object and of the object itself should be made, since these facts may be of the utmost importance in any trial resulting from the investigation. No one should handle an object other than the examiner himself. Portable articles removed should be labeled or marked so that they may be readily identified thereafter. The beam of a flashlight played over the surface of an object will frequently show the location of latent impressions, although this is not an infallible test for their presence. Evidence should be examined as soon as feasible after its discovery.