The pedigree of the human race / by Harris Hawthorne Wilder.

  • Harris Hawthorne Wilder
Date:
[1926?]
Catalogue details

Licence: In copyright

Credit: The pedigree of the human race / by Harris Hawthorne Wilder. Source: Wellcome Collection.

    40/394 page 20
    reduction of the size of the teeth. In many species the males develop large canines to be used as weapons, and in these cases the jaws also are heavier, producing a noticeable sexual difference. Claws vs. Nails. In at least one of the digits the typical mam- malian claw, which is curved, and laterally compressed, becomes transformed into a thin plate, flattened the other way, or dorso- ventrally, thus forming a typical nail, like those of Man. This change appears to have been brought about in correlation with the Primate method of grasping the limbs of trees, which applies the pressure in such a way as to constantly flatten the terminal phalanges of the digits. In the higher Primates all of the claws become thus transformed, while in the lower members of the Order at least one digit has a nail. Opposabl first digit. The first digit, especially that of the hind foot, shows a tendency to become separated from the rest by a considerable interval, and to have a greater freedom of motion. In this the joint especially affected is the one between the proximal end of the metacarpal, or metatarsal, and the associated carpal, or tarsal, bone (trapezium or internal cuneiforme). When typically developed the digit in question is enabled, not only to stand out markedly from the others, but to rotate in such a way as to oppose them, and, in the act of grasping a cylindrical object, to be placed along the side opposite to that in contact with the other digits. This opposition of the first digit seems to have been first acquired by the hind feet, and may well have been a pre-primate character, as it appears in certain marsupials, but in the lemurs and many of the Anthropoidea it is exhibited in the fore feet as well. In Man the opposable power of this digit in the case of the hind foot has become lost, evidently in adaptation to walking on the surface of the earth.1 Flair. This is in general quite thick and evenly distributed over the surface of the body as in typical mammals, but in the larger and more manlike forms it is sparse, especially ventrally, and there occur certain large areas which may be nearly or quite bare. The Ht may here be noted that opposability, i. e., the power of rotating the digit so as to place its distal end in opposition to the distal ends of the others, and the ability to separate the digit from its fellows, although usually con- nected, are two distinct things, and that while in certain primitive human races the great toe is remarkably distinct from the rest, it seems never to be truly opposable.
    digitised image 1
    digitised image 2
    digitised image 3