Pedagogical Anthropology, Maria Montessori [online e book reader TXT] 📗

at least, when the latter is not too much hidden by the hair, as often happens in the case of young children.

A knowledge of the normal forms of the cranium will also guide us in our judgment of many abnormal forms, which very often present the appearance of exaggerations of normal types.

Thus, for example, the acrocephalic cranium (much raised in the parieto-lambdoideal region and sloping forward toward the brow, while the occipito-lambdoideal region is flattened) recalls the trapezoid; and the clinocephalic cranium (in which the coronal suture forms a slight girdle-like indenture and divides the contour of the cranium, when observed along the vertical norm, in two curves, a lesser anterior and a greater posterior curve, resembling a figure of 8) recalls certain varieties of ovoid cranium described by Sergi. This brings us to a principle that is very interesting to establish, namely, that frequently anomalies represent exaggerations of the racial or family type.

The Cephalic Index

Retzius was the first to take the cranium under consideration as a basis for a classification of the human races; and he attempted to determine a concept of its form by means of a numerical formula expressing the relation between the length and width of the cranium (cephalic index). Thus he distinguished the races into brachycephalics, or those having a short head; and dolichocephalics, or those having a long head. Following Retzius, who may be regarded as the founder of craniology, Broca adopted, completed and expanded this method, deriving from the cranium, or rather from the particular character given by the cephalic index, a key, as it were, suited to unlocking the intricate mysteries of hybridism among the human races. Consequently the cephalic index was not confined, as regards its importance, within the same limits as all the other indexes, but was raised by the French school, warmly seconded by Italian anthropologists, to the dignity of a fundamental determinant of the ethnic type, as definitely as, for example, the vertebral column serves as basis for a classification including all species of vertebrates.

The Germans refused to accept the cephalic index as determining the classification of races; but while seeking to prove themselves independent of it, they continued to regard the form of the cranium as a basis of classification (Rütimeyer, von Höller, and to-day Virchow), but without ever having identified, as Sergi has now done, existing forms as normal types of race.

The cephalic index is obtained by the well-known formula expressing the relation between the maximum transverse diameter of the skull (see "Technique") and the maximum longitudinal diameter reduced to 100, and is expressed as follows: Ci = 100×d/D (the cephalic index is equal to a hundred times the lesser diameter divided by the greater; in the present case the lesser diameter is the transverse).

This proportion between linear measurements cannot properly sum up the form of the cranium. We can, for example, conceive of a microcephalic cranium having a normal cephalic index, since the relation between the two maximum diameters necessary for deducing the index, does not tell us, for example, either the dimension of the cranium or the form of the forehead.

If, for instance, we should imagine a photograph of a cranium enlarged a hundred diameters, the reciprocal relations between the length and the width would still remain unchanged.

In order to demonstrate that the cephalic index does not determine the form of the cranium, Sergi makes use of a number of different geometric figures, such as a triangle, an ellipse, a trapezoid inscribed within equal rectangles, and which consequently have an equal base and equal altitude, that is, the same proportion between length and width.

It follows that skulls corresponding more or less closely in shape, trapezoidal, trigonocephalic, ellipsoidal, plagiocephalic, and hence both normal and abnormal, can be expressed by a cephalic index having the same identical figures.

But, although the cephalic index is far from being descriptive in regard to the form of the cranium, it constitutes an anthropological datum that has two advantages: 1. It depends upon measurements and is therefore accessible to those who, not being anthropologists, lack the trained eye that can distinguish with careful accuracy the true forms of the cranium in their manifold variety. Furthermore, since the measurement of maximum diameters is sure and easy and may be obtained with exactness, regardless of the thickness of the hair, it may be applied in anthropological research to all subjects. 2. The cephalic index, even if it does not give us the form, does give us a fact which has a bearing upon the form, namely, whether the cranium is long or short; in other words, it substantially represents the most real and evident difference between the different types of cranium. And since the cranium has a visibly spheroid form, that is, with smooth and rounding surfaces, and constantly adheres to this generic delineation, the fact of being longer or shorter introduces a definite differentiation into the general and accepted form, and gives a very simple and concise indication of it, that conveys the idea more clearly than a description would.

Granting the practicality of this line of research, the cephalic index may also be accepted as an index of form, so long as there is no intention of going deeply into minute differentiations for systematic purposes. Professor Sergi himself, author of the system that forms the basis of the study of cranial forms, urged me to exclude from a practical course in pedagogic anthropology the classification of forms, limiting the concept of form to that included in the cephalic index.

The cephalic index has the additional advantage of having been extensively studied and consequently of having an abundance of mean averages for comparison that are of great practical use. Furthermore, the idea it gives regarding the cranium by means of one simple figure serves to convey certain fundamental principles with great clearness.

In dealing with figures that determine an anthropological datum of such high importance, it is necessary to define its limits and its nomenclature.

Various authors have introduced their own personal classification of the cephalic index, and no small confusion in nomenclature has resulted; so much so that a need was felt of establishing a uniformity of numerical limits and of the relative terminology, in other words, of simplifying the scientific language.

Accordingly, a congress was held at Frankfort in 1885, at which the following nomenclature was established by international agreement:

CEPHALIC INDEX.—Nomenclature established at Frankfort Dolichocephalia = 75 and below Mesaticephalia = from 75.1 to 79.9 Brachycephalia = from 80 to 85 Hyperbrachycephalia = 85.1 and above.

Previous to this, the most widely varied classifications were in use, and the leading authorities had all introduced into the literature of the subject their own personal classifications. Here are some of the more important:

Broca: Dolichocephalics = 75 and below Subdolichocephalics = from 75 to 80 Subbrachycephalics = from 80 to 83.3 Brachycephalics = 83.3 and above. Ranke: Dolichocephalics = 74.9 Mesaticephalics = from 75 to 79.9 Brachycephalics = 80 and above. Kollman: Dolichocephalics = 73.9 and below Mesaticephalics = from 74 to 79.9 Brachycephalics = from 80 to 86.9 Hyperbrachycephalics = 87 and above. Retzius and Davis: Dolichocephalia = 79 and below Brachycephalia = 80 and above. Topinard: Dolichocephalics 64 and below = Ultradolichocephalics. 65 True dolichocephalics. 66 67 68 69 70 Subdolichocephalics. 71 72 73 74 Mesaticephalics 75 True mestaicephalics 76 77 (Mean average.) 78 Submesaticephalics 79 Brachycephalics 80 Subbrachycephalics. 81 82 83 84 85 True brachycephalics. 86 87 88 89 90 and above = Ultrabrachycephalics.

It remains to determine the extreme limits of oscillation of the index, both in relation to the normal mean and in relation to the fluctuations of this important ethnic datum in a given population.

Topinard, as we have seen, gives as his mean figures for the extreme normal limits among the human races 64 and 90.

Deniker gives, as his mean averages for the human races, the following figures: For dolichocephaly, 69.4 (natives of the Caroline Islands; Australia); For brachycephaly, 88.7 (the Ayssori of the Transcaucasus; Asia).[37] But we know that a mean is obtained from figures either greater or smaller than the mean itself, so that the limits of individual variation must exceed that of the given figures.

Accordingly the oscillation of the normal cephalic indices may be given as ranging from 70 to 90.

In regard to abnormalities (extreme human limits of the cephalic index) the authorities give 58 for dolichocephaly (scaphocephaly) and 100 for brachycephaly (in which case the cranium is round and known as trochocephalic; it is met with among the insane).

Between oscillations of such extremely wide range in the normal cephalic index, the number chosen as a medial figure to serve the purpose of dividing the dolichocephalics from the brachycephalics is that of 80, which is included within the division of brachycephaly. In spite of the nomenclature established at Frankfort, there is a distinct scholastic advantage, because of the greater simplicity of memorising and fixing the idea, in reverting to the nomenclature of Retzius, who classes as brachycephalics all crania from 80 upward, and as dolichocephalics all those below 80. It is certainly strange to class all crania from 80 to 90 without distinction as brachycephalics, and then to alter the name and call a cranium with an index of 79.9 a dolichocephalic. It has been found that there is always a slight difference between the index taken from measurements of the cranium and that obtained from measurements of the head. According to Broca, it is necessary to subtract two units from the cephalic index taken from a living person, in order to obtain that of the cranium; thus, for example, if the cephalic index (taken from life) is 80, the cranial index (taken from the skeleton) would be 78. Such differences are due to the disposition of the soft tissues. Consequently, even according to the simple subdivision of Retzius, a person who was brachycephalic during life, would become dolichocephalic after he was dead.

But this is what always happens in biology, whenever we try to establish definite limits. Life undergoes an insensible transition through successive limits and forms, and this fact constitutes the grave difficulties and the apparent confusion of biological systems. In determining degrees of difference, it is necessary to have recourse constantly to special methods, which teach us to recognise general properties and to use them as a basis in dividing living creatures into separate groups (see in the section on Method, "Mean measurements and formation of series in relation to individual variations").

Hence, for mnemonic purposes, we need remember only the single number, 80.

But if we wish to adopt the nomenclature of Frankfort, it is necessary to keep in mind two figures denoting limits, 75 (inclusive) for dolichocephaly, and 80 (inclusive) for brachycephaly.

75 dolichocephalics mesaticephalics 80 brachycephalics 85 ultra

These constitute, as it were, two centres, beyond which, on this side and on that, we may picture to ourselves the individual variations drawn up in martial line. In this case, the space between 75 and 80, in other words, the limits of mesaticephaly, may be interpreted as due to oscillations between dolicho- and brachycephaly according to the laws of variability, which is analogous to what takes place in the case of oscillations in the opposite direction (70-75 dolichocephaly; 80-85 brachycephaly). From this point of view, these two numbers, 75 and 80, constitute median centres of two different types.

But according to Broca and his school—and this view is accepted by many anthropologists—mesaticephaly should be regarded as constituting a fusion of the two other types, the brachy- and dolichocephalic, whence it follows that mesaticephalics would be hybrids. Other authorities, on the contrary, exaggerating the conception of the fixity of the cephalic index in a given race, admit the existence of mesaticephalic races.