Fig. 70.—Left hand of chacma baboon.
Fig. 70 of the Chacma baboon, playfully called by the Boers Adonis, is a very active and wary animal which lives on the rough rocky slopes of the Cape. It is very much of a pedestrian and the response of its mode of life and use of its forefoot is shown in five great pads of muscle and efficient whorls of ridges for touch, those on the digits being very nearly all transverse in accordance with simple flexion of these joints. This again is what one would expect if my hypothesis be sound. The purely non-slipping mechanism supposed by the rival view is not here well supported by the facts.
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. | ||