« PrécédentContinuer »
The results are classified into three groups :
1. Dolichocephalic, with an index below 75: Australians, Kaffirs, Zulus, Eskimo, Fijians. 2. Mesaticephalic, ranging from 75 to 80: Europeans (mixed), Chinese, Polynesians (mixed). 3. Brachycephalic, with an index over 80: Malays, Burmese, American Indians, Anda
In order to provide for uniformity in the results of different observers, some system is necessary by which the various points from which the measurements are taken must correspond. Whilst there is much difference in the value of the measurements insisted on by individual anatomists, all agree in endeavouring to select such points on the skull as may be readily determined, and which have a fairly fixed anatomical position. The more important of these "fixed points" are included in the subjoined table :
Nasion. The middle of the naso-frontal suture.
Glabella. A point midway between the two superciliary ridges.
Ophry on. The central point of the narrowest transverse diameter of the forehead, measured from one temporal line to the other.
Inion. The external occipital protuberance.
Maximum Occipital Point.-The point on the squamous part of the occipital in the sagittal plane most distant from the glabella.
Opisthion. The middle of the posterior margin of the foramen magnum.
Subnasal Point.-The middle of the inferior border of the piriform (anterior nasal) aperture at the centre of the anterior nasal spine.
Akanthion. The most prominent point on the nasal spine.
Vertex. The summit of the cranial vault.
Obelion. A point over the sagittal suture, on a line with the parietal foramina.
Pterion. The region of the antero-lateral fontanelle where the angles of the frontal, parietal, squamous part of the temporal, and great wing of sphenoid lie in relation to one another. As a rule, the sutures are arranged like the letter H, the parietal and great wing of sphenoid separating the frontal from the squamous temporal. In other cases the form of the suture is like an X; whilst in a third variety the frontal and squamous part of the temporal articulate with each other, thus separating the great wing from the parietal.
Asterion is the region of the postero-lateral fontanelle where the lambdoid, parieto-mastoid, and occipito-mastoid sutures meet.
Stephanion. The point where the coronal suture crosses the temporal line. Dacryon. The point where the vertical lacrimo-maxillary suture meets the fronto-nasal suture at the inner angle of the orbit.
Jugal Point.-Corresponds to the angle between the vertical border and the margin of the
Supra-auricular Point.-A point immediately above the middle of the orifice of the
Pogonion. The most prominent point of the chin as represented on the mandible.
The measurements of the length of the skull may be taken between a variety of points-the nasion, glabella, or ophryon in front, and the inion or maximum occipital point behind. Or the maximum length alone may be taken without reference to any fixed points. In all cases it is better to state precisely where the measurement is taken. The maximum breadth of the head is very variable as regards its position; it is advisable to note whether it occurs above or below the parieto-squamosal suture. The inter-relation of these measurements as expressed by the cephalic index has been already referred to. The width of the head may also be measured from one asterion to the other, biasterionic width, or by taking the bistephanic diameter.
The height of the cranium is usually ascertained by measuring the distance from the basion to the bregma. The relation of the height to the length may be expressed by the height or vertical index, thus
Height x 100 - Vertical index.
Skulls are classified in accordance with the relations of length and height as follows:
Tapeinocephalic index below 72.
Metriocephalic index between 72 and 77.
Chamæcephalic index up to 70.
The horizontal circumference of the cranium, which ranges from 450 mm. to 550 mm., is measured around a plane cutting the glabella or ophryon anteriorly, and the maximum occipital point posteriorly. The longitudinal arc is measured from the nasion in front to the opisthion behind; if to this be added the basi-nasal length and the distance between the basion and the opisthion, we have a record of the vertico-median circumference of the cranium. This may further be divided by measuring the lengths of the frontal, parietal, and occipital portions of the superior longitudinal arc. In this way the relative proportions of these bones may be expressed.
The measurements of the skeleton of the face are more complex, but, on the whole, of greater value than the measurements of the cranium. It is in the face that the characteristic features of race are best observed, and it is here that osseous structure most accurately records the form and proportions of the living.
The form of the face varies, like that of the cranium, in the relative proportions of its length and breadth. Generally speaking, a dolichocephalic cranium is associated with a long face, whilst the brachycephalic type of head is correlated with a rounder and shorter face. This rule, however, is not universal, and there are many exceptions to it.
The determination of the facial index varies according to whether the measurements are made with or without the mandible in position. In the former case the length is measured from the ophryon or nasion above to the mental tubercle below, and compared with the maximum bizygomatic width. This is referred to as the total facial index, and is obtained by the
Ophryo-mental length × 100
Ophryo-alveolar length x 100
-Total facial index.
More usually, however, owing to the loss of the mandible, the proportions of the face are expressed by the superior facial index. This is determined by comparing the ophryo-alveolar or naso-alveolar length with the bizygomatic width, thus—
= Superior facial index.
The terms dolichofacial or leptoprosope and brachyfacial or chamoprosope have been employed to express the differences thus recorded.
Uniformity in these measurements, however, is far from complete since many anthropologists compare the width with the length = 100.
The proportion of the face-width to the width of the calvaria is roughly expressed by the use of the terms cryptozygous and phænozygous as applied to the skull. In the former case the zygomatic arches are concealed, when the skull is viewed from above, by the overhanging and projection of the sides of the cranial box; in the latter instance, owing to the narrowness of the calvaria, the zygomatic arches are clearly visible.
The projection of the face, so characteristic of certain races (Negroes for example), may be estimated on the living by measuring the angle formed by two straight lines, the one passing from the middle of the external acoustic meatus to the lower margin of the septum of the nose; the other drawn from the most prominent part of the forehead above to touch the incisor teeth below. The angle formed by the intersection of these two lines is called the facial angle Camper), and ranges from 62° to 85°. The smaller angle is characteristic of a muzzle-like
projection of the lower part of the face. The larger angle is the concomitant of a more vertical profile. The degree of projection of the maxilla in the macerated cranium is most commonly expressed by employing the gnathic or alveolar index of Flower. This records the relative proportions of the basi-alveolar and basi-nasal lengths, the latter being regarded as= = 100,
Basi-alveolar length x 100
The results are conveniently grouped into three classes:
Orthognathous, index below 98: including mixed Europeans, ancient Egyptians, etc.
Unfortunately, however, little reliance can be placed on the results obtained by this method, since it takes no account of the proportion of the third or facial side of the gnathic triangle. For a further discussion of this matter see Thomson and MacIver, Races of the Thebaid (Oxford: Clarendon Press, 1905).
The form of the piriform aperture in the macerated skull is of much value from an ethnic standpoint, as it is so intimately associated with the shape of the nose in the living. The greatest width of the aperture is compared with the nasal height (measured from the nasion to the lower border of the aperture) and the nasal index is thus determined :—
Nasal width x 100
Leptorhine, with a nasal index below 48: as in mixed Europeans, ancient Egyptians,
American Indians, etc.
Mesorhine, with an index ranging from 48 to 53: as in Chinese, Japanese, Malays, etc. Platyrhine, with an index above 53: as in Australians, Negroes, Kaffirs, Zulus, etc.
The form of the orbit varies considerably in different races, but is of much less value from the standpoint of classification. The orbital index expresses the proportion of the orbital height to the orbital width, and is obtained by the following formula :—
Orbital height × 100
The orbital height is the distance between the upper and lower margins of the orbit at the middle; whilst the orbital width is measured from a point where the ridge which forms the posterior boundary of the lacrimal groove meets the fronto- lacrimal suture (Flower), or from the dacryon (Broca) to the most distant point from these on the anterior edge of the lateral border of the orbit.
The form of the orbital aperture is referred to as—
Megaseme, if the index be over 89;
Mesoseme, if the index be between 89 and 84;
The variations met with in the form of the palate and dentary arcade may be expressed by the palato-maxillary index of Flower. The length is measured from the alveolar point to a line drawn across the posterior borders of the maxillæ, whilst the width is taken between the outer borders of the alveolar arch immediately above the middle of the second molar tooth. To obtain the index, the following formula is employed :
For purposes of classification Turner has introduced the following terms:
Dolichuranic, index below 110.
Mesuranic, index between 110 and 115.
Palato-maxillary width × 100
As is elsewhere stated the size of the teeth has an important influence on the architecture of the skull. Considered from a racial standpoint, the relative size of the teeth to the length of the cranio-facial axis has been found by Flower to be a character of much value. The dental length is taken by measuring the distance between the anterior surface of the first premolar and the posterior surface of the third molar of the upper jaw.
To obtain the dental index the following formula is used:
Following the convenient method of division adopted with other indices, the dental indices may be divided into three series, called respectively
Microdont, index below 42: including the so-called Caucasian or white races.
Many complicated instruments have been devised to take the various measurements required, but for all practical purposes the calipers designed by Flower or the compas glissière of Broca are sufficient.
As an aid to calculating the indices, the tables published in the Osteological Catalogue of the Royal College of Surgeons of England, Part I., Man; Index- Tabellen zum anthropometrischen Gebrauche, C. M. Furst, Jena, 1902; or the index calculator invented by Waterston will be found of much service in saving time.
(2) Indices and Measurements of other Parts of the Skeleton.
In addition to the indices employed to express the proportions of the cranial measurements, there are others similarly made use of to convey an idea of the proportions of different parts of the skeleton. Of these the following may be mentioned as those in most common use:
Scapula. At birth the form of the human scapula more closely resembles the mammalian type in that its breadth, measured from the glenoid cavity to the vertebral border, is greater in comparison with its length than in the adult. This proportion is expressed as follows:—
Breadth from glenoid cavity to vertebral border x 100
The index ranges from 87 in African pygmies, which therefore have proportionately broader scapulæ, to 61 in Eskimos. The average European index is about 65.
Hip Bone. The relation of the breadth of this bone to its height is computed as follows::--
Iliac breadth x 100
- Innominate index.
Man as compared with the apes is distinguished by possessing proportionately broader and shorter hip bones. The index in man ranges from 74 to 90.
Pelvis. The form of the human pelvis is characterised by an increased proportionate width and a reduced proportionate height or length. The relation of these diameters is expressed by the formula :
Pelvic breadth-height index.
Ischio-iliac height x 100
Greatest breadth between the outer lips of the iliac crests
The average index for white races is 73.
Pelvic Cavity. The measurements usually taken are those of the superior aperture. man there is a proportionate increase in the transverse diameter as compared with lower forms :Antero-posterior diameter (conjugate) from mid-point of sacral promontory to the posterior margin of pubic symphysis × 100 Greatest transverse width between ilio-pectineal lines
Turner has classified the indices into three groups :
Pelvic or brim index.
Dolichopellic, index above 95: Australians, Bushmen, Kaffirs.
Sum of posterior vertical diameters of the bodies of five lumbar
Vertebral Column.-A characteristic feature of man's vertebral column is the pronounced lumbar curve associated with the erect posture in the living. Apart from the consideration of the interposition of the intervertebral fibro-cartilage between the segments, the bodies of the lumbar vertebræ influence and react on the curve by exhibiting differences in their anterior and posterior vertical diameters. Advantage has been taken of this to endeavour to reconstruct the lumbar curve from the dried and macerated bones, but it must be borne in mind that habitual posture or increased range of movements may yield results which are possibly misleading. Thus there is reason for believing that the squatting position, when habitually adopted, may give rise to a compression of the anterior parts of the bodies of the vertebra which it might be assumed was associated with an absence of or flattening of the lumbar curve, which in fact did not exist during life.
The quality of the curve is estimated from the macerated bones by an index which is computed as follows:
- General lumbar index.
The results are classified as follows:
Kurtorachic, index below 98, displaying a forward convexity: includes Europeans
Orthorachic, index between 98 and 102, column practically straight includes examples
of Eskimo and Maori.
Koilorachic, index above 102, displaying a backward convexity includes Australians,
Sacrum.-Man's sacrum is characterised by its great breadth in proportion to its length. These relations are expressed as follows:
Greatest breadth of base of sacrum x 100
Length from middle of promontory to middle of anterior inferior border of fifth sacral vertebræ
The diverse forms are grouped as follows:—
Dolichohieric, index below 100, sacra longer than broad: includes Australians, Tasmanians,
Platyhieric, index above 100, sacra broader than long: includes Europeans, Negroes,
Limb Bones. The proportionate length of the limb bones to each other and to the body height is of practical interest. It is a matter of common knowledge that the forearms of Negroes are proportionately longer than those of Europeans. Great differences, too, are met with in the absolute and proportionate length of the lower limbs, nor must the relation of these to body height be overlooked. An enumeration of the more important of these indices, and the manner of their computation, will suffice. The proportion of the length of the radius to the length of the humerus is expressed as follows:
Sub-divided into three groups :-
Brachykerkic, index less than 75: includes Europeans, Lapps, Eskimo.
Mesatikerkic, index between 75-80: Chinese, Australians, Polynesians, Negroes. Dolichokerkic, index above 80: Andamanese, Negritoes and Fuegians, Bonindae in general. The proportion of the length of the tibia to the femur is computed by the formulaLength of tibia from surface of condyle to articular surface for talus × 100 Oblique length of femur
= Sacral index.
Sub-divided into two groups :
Brachyknemic, index 82 and under: includes Europeans and Mongolians generally.
The proportion of the length of the upper limb to that of the lower limb is obtained thus:-
Length of humerus x 100
A comparison between the relative lengths of the upper segments of the limbs is obtained by the following formula:—
- Humero-femoral index.
Platymeria (see p. 281).-The amount of compression of the femur is estimated as follows:-
= Platymeric index.
Platyknemia (see p. 281)-The degree of compression of the tibia is estimated by the
Transverse diameter of shaft at level of nutrient foramen × 100
The index ranges from 60 in a Maori tibia to 80 to 108 in modern French tibiæ.
For further and more detailed information relating to the various measurements and indices employed by the physical anthropologist, the reader is referred to Topinard's Elements d'Anthropologie; Sir W. Turner's Challenger Memoirs, Part 47, vol. xvi.; and Duckworth's Morphology and Anthropology.