The palmar surface of the hands and the soles of the feet, both in men and monkeys, are covered with minute ridges that bear a superficial resemblance to those made on sand by wind or flowing water. They form systems which run in bold sweeps, though the courses of the individual ridges are less regular. Each ridge (Plate 3, Fig. 5) is characterised by numerous minute peculiarities, called _Minutiae_ in this book, here dividing into two, and there uniting with another (_a_, _b_), or it may divide and almost immediately reunite, enclosing a small circular or elliptical space (_c_); at other times its beginning or end is markedly independent (_d_, _e_); lastly, the ridge may be so short as to form a small island (_f_). Whenever an interspace is left between the boundaries of different systems of ridges, it is filled by a small system of its own, which will have some characteristic shape, and be called a _pattern_ in this book. [Illustration: PLATE 3. FIG. 5. Characteristic peculiarities in Ridges (about 8 times the natural size). FIG. 6. Systems of Ridges, and the Creases in the Palm.] There are three particularly well-marked systems of ridges in the palm of the hand marked in Plate 3, Fig. 6, ~1~, as Th, AB, and BC. The system Th is that which runs over the ball of the thumb and adjacent parts of the palm. It is bounded by the line _a_ which starts from the middle of the palm close to the wrist, and sweeps thence round the ball of the thumb to the edge of the palm on the side of the thumb, which it reaches about half an inch, more or less, below the base of the fore-finger. The system AB is bounded towards the thumb by the above line _a_, and towards the little finger by the line _b_; the latter starts from about the middle of the little-finger side of the palm, and emerges on the opposite side just below the fore-finger. Consequently, every ridge that wholly crosses the palm is found in AB. The system BC is bounded thumbwards by the line _b_, until that line arrives at a point immediately below the axis of the fore-finger; there the boundary of BC leaves the line _b_, and skirts the base of the fore-finger until it reaches the interval which separates the fore and middle fingers. The upper boundary of BC is the line _c_, which leaves the little-finger side of the palm at a small distance below the base of the little finger, and terminates between the fore and middle fingers. Other systems are found between _c_ and the middle, ring, and little fingers; they are somewhat more variable than those just described, as will be seen by comparing the five different palms shown in Fig. 6.