I possess a few specimens of hand prints of persons taken when children, and again, after an interval of several years: they show a general accordance in respect to the creases, but not sufficiently close for identification.
The ridges on the feet and toes are less complex than those on the hands and digits, and are less serviceable for present purposes, though equally interesting to physiologists. Having given but little attention to them myself, they will not be again referred to.
The ridges are studded with minute pores which are the open mouths of the ducts of the somewhat deeply-seated glands, whose office is to secrete perspiration: [Plate 10], n, is a good example of them. The distance between adjacent pores on the same ridge is, roughly speaking, about half that which separates the ridges. The lines of a pattern are such as an artist would draw, if dots had been made on a sheet of paper in positions corresponding to the several pores, and he endeavoured to connect them by evenly flowing curves; it would be difficult to draw a pattern under these conditions, and within definite boundaries, that cannot be matched in a living hand.
The embryological development of the ridges has been studied by many, but more especially by Dr. A. Kollmann,[1] whose careful investigations and bibliography should be consulted by physiologists interested in the subject. He conceives the ridges to be formed through lateral pressures between nascent structures.
PLATE 4.
Fig. 7.
SCARS and CUTS, and their Effects on the Ridges.
| a Effect of an Ulcer. | b Finger of a Tailor. | c Effect of a Cut. |