There are important points connected, with the printing of finger-patterns, especially for legal investigation, which come now to be considered. A human finger, as we have seen, is not, for printing purposes, just like a lithographic stone, a box-wood engraving, or a plate of zinc, steel, or copper. In ordinary printing, especially of high-class and delicate engravings, the quality and fluency of ink, the smoothness of surface and hygrometric conditions of paper--due sometimes to local atmosphere, and sometimes to climate generally--the skill of workmen, all the conditions co-operate in producing variations, slight it may be, but noticeable in the results obtained. In the case of finger-prints we might also have to consider the willingness or unwillingness of the subject having his finger-prints officially taken. A finger--even that of a dead person--is compressible, while retaining on the whole the pattern of its furrows and ridges, and hence under fairly similar conditions, the printed products may be somewhat different in appearance. The same fact would apply, no doubt, also to impressions taken from an indiarubber stamp, made, we shall suppose, for stamping purposes in regard to documents, in imitation of a particular finger-print pattern. Greater compression tends to flatten out the ridges and to narrow the intervening grooves, while it may also tend, especially when associated with over-inking, to obliterate some of the characteristic ramifications of the pattern. But, again, the finger of a living person is usually in a state of physiological activity. It swells or shrinks, drying up or exuding moisture from its many pores, which facts, however minute and insignificant they may appear to the uninstructed, to the trained dactylographer they leave a most interesting and significant record behind.