In the tibia attention has been called to platycnemia—that is to say, the transversal flattening in the upper third of the diaphysis of the bone, so that its posterior side becomes transformed into a border. It has been supposed that this form is a reversion towards the simian type, but Manouvrier[87] has shown that platycnemia never attains in the anthropoid apes the degree which it presents in the human race, where it is due especially to the development of the tibialis posticus muscle which plays a great part in the maintenance of the upright position, and in the movements of walking and running. The degree of platycnemia may thus vary according to the more or less sedentary or wandering habits of the different populations.
The retroversion of the head of the tibia—that is to say, the slope of the articular surface of it behind—pointed out and described for the first time by Collignon in prehistoric tibias, is also not a simian character. According to Manouvrier,[88] it is often met with among Parisians in a degree superior to that exhibited by anthropoid apes. This retroversion, generally associated with platycnemia, is connected with the half-bending attitude of the lower limb in the manner of walking which is called the bending gait, common among peasants, and especially mountaineers. The retroversion is more marked in the tibia of the new-born child than in that of the adult, and this appears to have a connection with the permanent bending of the knee during intra-uterine life.
The length of the bones of the pelvic and thoracic limbs varies according to race, but it is difficult to establish the degree of these variations, owing to the small number of observations made. Besides, we can more profitably substitute for measurements of limbs on the skeleton those of the living subject; in the latter case we can at least relate all the measurements to the true height of the subject, whilst the height is never exactly known from the skeleton.
However, the measurements of the long bones have their importance, for they permit us to reconstitute approximately, as we have already seen (p. [33]), the height of subjects of which we have only the bones, as is the case of all populations that have preceded us.
It is for this reason that I give the following figures derived from nine series of from five to seventy-two skeletons. The length of the humerus represents from 19.5 (Polynesians) to 20.7 per cent. (Europeans) of the height of the skeleton; that of the radius from 14.3 (Europeans) to 15.7 (Negroes); that of the femur from 26.9 (South Americans) to 27.9 (New Caledonians); lastly, the length of the tibia represents from 21.5 (Esthonians) to 23.8 per cent. (New Caledonians) of the height of the skeleton. Thus the differences are insignificant, and the variations between race and race do not extend beyond the limits of a unit and a half for each of the bones.
The length of the radius in relation to the humerus (= 100) exhibits variations a little more appreciable. It is 72.5 among Europeans, 76 among New Caledonians, 79 among Negroes, 79.7 among Veddahs, 80.6 among Fuegians, 81.7 among Andamanese. Let us note that the fore-arm, relatively to the arm, is much longer in the fœtus in the first stages of development and in early infancy than in the adult;[89] it is shortened in proportion to the height as the fœtus and the infant grow.
Proportions of the Body in the Living Subject.—In spite of the quantity of material accumulated, we have not been able up to the present to make any use of the differences which these proportions exhibit according to race. The reason is that these differences are very trifling. In order to understand this proposition better I will give by way of illustration the proportions which we may consider as nearly normal in a European of average stature (1 m. 65, or 5 ft. 5 ins.). Topinard established thus the principal proportions of the European,[90] assuming the height = 100.
| Head | 13 |
| Trunk and neck | 35 |
| (32.7 without neck.) | |
| Thoracic limb | 45 |
| Arm | 19.5 |
| Forearm | 14 |
| Hand | 11.5 |
| Abdominal limb | 47.5 |
| (from the ischiatic plane to the ground.) | |
| Foot | 15 |
| Span of arms (middle finger of one hand to middle finger of the other.) | 104.4 |
The proportions in the different populations of the earth oscillate round these figures without diverging from them more than three units, or five at most. Thus, for example, the proportions of the height of the head vary between 11.4 and 15, according to Rojdestvensky;[91] the proportions of the trunk without the neck from 32.6 to 32.8, according to Topinard, etc.