/anthropology/glossary/height-length-index
The height-length index is the height of the skull expressed as a percentage of its length. It is the companion of the cephalic index, with which it shares its denominator, and it sets the vertical dimension of the braincase against the length in place of the transverse. The classical literature recorded it in every craniometric table and seldom made it a criterion of type; the corpus's source does make it one, on the ground that the height of the skull is the less plastic of the two measures. Whether that ground holds is the question this entry comes to.
Status: Preliminary. Martin's boundaries are given from the handbook; the corpus's source names three classes without stating its cuts.
chamae- χαμαί on the ground, low · ortho- ὀρθός upright · hypsi- ὕψι high · -cranic κρανίον skull · -cephalic κεφαλή head
A low index is a low skull, chamaecranic; a high index a high skull, hypsicranic; and orthocranic lies between. Here the suffix carries real information, and the first principle of the front page applies in its clearest form. The index is defined from the basion, a point on the rim of the foramen magnum that no instrument reaches on a living head; living measurements therefore substitute another landmark and another scale, and the handbooks mark the substitution by writing -cephalic. The corpus's source writes -cranic throughout and gives its reason, that the measure belongs to the skull and the living forms only approximate it.
Height is taken from the basion, the midpoint of the front margin of the foramen magnum, to the bregma, where the coronal and sagittal sutures meet at the top of the vault. Length is the cephalic index's length, from the glabella to the opisthocranion. Both are taken with the spreading caliper, on bone.
Since the basion is inaccessible on the living, height is there taken from the tragion, the notch above the tragus of the ear, to the vertex, with the head held in the Frankfurt plane. This auricular height is shorter than the basion-bregma height by the depth of the skull base, and the auricular index accordingly runs some twelve to fifteen units below the cranial one. The two indices cannot be read on one scale, and the handbooks give each its own cuts.
| Class | Skull, basion–bregma, Martin (1914) | Living, auricular, Martin (1914) | Human Phenotypes, skull |
|---|---|---|---|
| chamae- | –69.9 | –57.9 | low skulls |
| ortho- | 70.0–74.9 | 58.0–62.9 | medium-high skulls |
| hypsi- | 75.0– | 63.0– | high skulls |
The source states a world mean near 74 and population means from 67 to 80. On Martin's scale that range is orthocranic almost throughout, with the world mean lying at the upper cut.
The source's usage implies a division other than Martin's, and the implication should be made explicit. More than half of the corpus's varieties are called hypsicranic; on Martin's scale, with its cut at 75, that class could hold only the upper tail of the world's populations. The source appears, then, to class populations against the world mean rather than against the handbook's absolute bounds, so that hypsicranic in the corpus means high for a population and not high on Martin's scale. The source does not state its cuts, and this reading rests on the counts alone; but a reader who carries Martin's bounds into the corpus will otherwise suppose the world's skulls higher than they are.
Height of the skull was among Broca's standard measurements, and the vertical index appears in his craniological instructions of 1875. Martin's handbook of 1914 fixed the basion-bregma and auricular scales. Thereafter the index was a column in every published skull series and a criterion in few typologies; Coon's Races of Europe of 1939 is one that used the height of the vault to separate types the cephalic index could not. The corpus's source follows Coon in this and goes further, placing nearly every variety on the index and giving it, as the next section discusses, a particular trust.
The index records a real dimension of the vault, and the means of populations differ by it. The source adds an observation that goes beyond the ratio: high skulls tend to a flat occiput and low skulls to a projecting one, so that the index is bound up with the whole form of the braincase and not with a single proportion.
It does not sort the great divisions of mankind, any more than its companion does. The source states that every continent has high-skulled and low-skulled groups, and that the variation between individuals inside a population exceeds that of the cephalic index. The index distinguishes neighbours and not continents, and the same limit that was set out under the cephalic index applies here.
The source's principal claim for the measure is that it is much less altered by conditions than the cephalic index, so that the brachycephalisation of Europe left it nearly unchanged. The claim is plausible and may be true, but it should be stated with the reservation it requires. Skull length is the denominator of both indices. A shortening of the skull raises the height-length index exactly as it raises the cephalic index, unless the height of the vault falls in step with the length; the source's claim therefore implies that it did, which is a statement about the vault's height and not about the index's steadiness. The handbooks do not settle the point. The medieval and modern series that document brachycephalisation would, and until they are consulted the claim stands as the source's and not as established.
Nor is the vault beyond the reach of custom. Cradle-boards and binding alter its height directly, and the high, short skulls of some American and Near Eastern series are the work of infancy rather than of descent. The caution given under the cephalic index applies without change.
Comparability between sources is the index's weakest point. A skull series and a living series yield different numbers for the same population, and a class name given without its landmark does not say which was used. The corpus's descriptions are skull values by the source's stated convention.
The judgment is that the index is a sound measure of the vault's form, informative between neighbouring populations and not beyond them, and probably steadier over time than the cephalic index, though the evidence for its steadiness is thinner than the source's confidence in it.
Of the 209 local varieties, 196 are placed on the index. A type written "chamae- orthocranic" straddles a cut and is counted under both classes.
| Class | Types | Examples |
|---|---|---|
| chamaecranic | 50 | Arabid, Bering Sea, Botocudo, Gobid |
| orthocranic | 84 | African Alpinoid, Alföld, Amur-Sakhalin |
| hypsicranic | 110 | Aetid, Aisto Nordid, Anatolid |
Twenty-eight types are written "chamae- orthocranic" and seven "ortho- hypsicranic"; one, Lagoa Santa, is given the living form hypsicephalic. The weight of the distribution toward the high end is the ground of the inference about the source's cuts drawn above.
The cephalic index, which shares this index's denominator and its question of plasticity. Head size, for the absolute dimensions both indices discard. The morpheme grid.
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