Neither the arrangements of ridges (Fig. 61), in _loris_, nor the _hedgehog_ (Fig. 62), nor the _squirrel_ (Fig. 63), need further reference, but they are all, I think, very consistent with the prolonged effects of use and habit. Some Undesigned Experiments in Ridges. This section of the subject has afforded a good supply of indirect evidence, but so far no direct proof that papillary ridges can be created and disposed in their lines by pressure, friction and response. The clearest case is one I brought forward at the Zoological Society of London in 1905, and which was published in its proceedings of April 18th. It was an instance of the hand of a _chimpanzee_ with papillary ridges produced in an aberrant or abnormal situation by walking, and was given as follows:-- “In the course of an examination of the papillary ridges in some specimens of anthropoid apes and monkeys certain groups of ridges were found on the _extensor_ surface of the terminal phalanges of the hand, apparently identical with those of the palmar and plantar surfaces. Three specimens of chimpanzee living in the Society’s menagerie were examined, of the ages: one year eight months, two-and-a-half years and six years. In the oldest of these, called “Mickie,” the ridges were definite and well-developed, on the second, third and fourth digits on both hands; in the youngest specimen, “Jack,” they were absent; and in “Jimmie,” two-and-a-half years old, they were small and ill-defined, as if in process of development. Direction of Ridges. _Mickie._ Ridges longitudinal and reaching to the matrix of the nail on the second, third and fourth digits. _Jimmie._ Showed ridges as follows:-- R. hand 1st D none. L. hand 1st D none. 2nd " oblique. 2nd " oblique. 3rd " transverse at base of D. 3rd " " 4th " " " " 4th " " 5th " nearly longitudinal. 5th " none. _In these three specimens ridges were absent from the corresponding surfaces of the foot._ “The well-defined longitudinal direction of the ridges in “Mickie” is worth notice. It must be remembered in this connection that a chimpanzee walks with the extensor surfaces of the phalanges touching the ground and the digits turned inwards, so that their long axis are at right angles to the line of progression of the animal, and accordingly the ridges of this part also occupy the same relative position. There is no correlation in this instance between the act of prehension and the direction of the ridges, though it agrees closely with the general rule which obtains in so many regions, that the ridges lie at right angles to the line of incidence of the predominating pressure on the part.”