Pedagogical Anthropology by Maria Montessori (best novels of all time TXT) 📕
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I = (100×m)/M
This formula of relations between measurements is of wide application in anthropology and is fundamental. Indices of every measurement are sought for. The one given above is the index of stature, and it determines the type of stature. All the other indices are calculated by similar procedure.
Fig. 145.—Method of measuring the total spread of arms.
Total Spread of the Arms.—This measurement is taken quite simply. The subject must place himself with his arms outstretched in a horizontal direction and on a level with his shoulders. The measurement corresponds to the distance intervening in a horizontal line from the tip of one middle finger to the other (Fig. 145). A specially constructed anthropometer may be used for this measurement. It has a long horizontal rod adjustable perpendicularly, so that it may be placed on a level with the shoulders of the subject to be measured. This rod forms a cross with the other vertical rod with which the subject should be in contact. The arms are then extended along the cross rod which is marked with a millimetric scale. But this greatly complicates the anthropometer, and hardly any anthropometer possesses this attachment. This measure may be successfully taken with the very simple aid of the wall. The only difficulty offered is that of securing a perfectly horizontal position for the arms. For this purpose horizontal lines, which either happen by chance to be upon the wall or which may be drawn on purpose, will be of assistance. In order to have guiding lines suited to different statures, several horizontal lines may be drawn intersecting the vertical line already traced for guidance of the millimetric tape measure used in taking the stature.
Thoracic Perimeter.—The thoracic perimeter is taken on the nude thorax, in an erect position and with the arms hanging beside the bust, by applying the millimetric measure in such a way that its upper margin passes just below the nipples. The tape measure should completely encircle the thorax in a horizontal plane passing through the mammary papillæ. Since the thorax is in constant motion, we must observe the oscillations of the tape measure and obtain the average; or else we may take the measurements during the state of expiration (repose). In giving the figure it is necessary to specify the procedure followed.
Vital Index. Index of Life.—Index of life is the name given to the proportion between the stature and the thoracic perimeter. It ought to be equal to 50, i.e., Tp = S/2
Vi = (100×Tp)/S = 50 (normal).
Weight.—The weight of an individual is taken by means of ordinary scales. In order to obtain the weight of the nude person, the clothing may be weighed separately and their weight subtracted from the total weight of the clothed person. The weight should be taken before eating, in order that unassimilated alimentary substances may not alter the real weight of the subject. If this method cannot be rigorously followed out, it should be specified how much clothing the subject retained, whether he had eaten, etc.
Ponderal Index.—Stature and weight are the most synthetic and comprehensive measurements of the form. But we need a clear proportion between these two measures to tell us whether an individual weighs more or less relatively to his stature. It may happen, for instance, that a stout person of short stature actually weighs less than another person who is tall and thin; but relatively to his stature he may on the contrary be heavier, that is, he may have a higher ponderal index. A robust and plump child will weigh in an absolute sense less than an adult who is extremely thin and emaciated; but relatively to the mass of his body he weighs more. Now this relative weight or index of weight (ponderal index) gives us precisely this idea of embonpoint, of the more or less flourishing state of nutrition in which an individual happens to be. But linear measurements such as the stature cannot be compared with volumetric measurements, such as the weight. Hence it is necessary to reduce the volumetric measure—the weight—to a linear measure, which is done by extracting the cube root from the number representing the weight. Then the root of the weight may be compared to the stature reduced to a scale of 100. By forming a general proportion, in which W represents the weight of a given individual, and S the corresponding figure of his stature, we obtain:
S:∛(W)::100:x (where x represents the ponderal index)
hence Pi = (100×∛(W))/S
The application of this formula would necessitate some rather complicated calculations, which it would be inconvenient to have to repeat for a large number of subjects.
But there are tables of calculations already compiled, which are due to Livi, and which are given, together with other tables, in Livi's own work, Anthropometry (Hoepli). These are numerical tables, to be read in the same manner as tables of logarithms. At the top, in a horizontal direction, the stature is given in centimetres, while in the vertical column the weight is given in kilograms. The calculation of all the ponderal indices has been worked out, in relation to every possible stature and weight. If we look up the ponderal index corresponding to the figures already cited in illustration (see p. (182)), we find that for the adult the Pi = 23.6, and for the child the Pi = 27.4; i.e., considered relatively the child weighs more in the given case. This is the true and accurate technical method of finding the relative proportion between weight and stature.
Accordingly, we have now learned to take all the measurements relative to the form, to calculate from them the more important indices (or proportions), such as the index of stature, the index of life, and the ponderal index. We have also learned to understand and to consult the tables of anthropological calculations.
The CraniumThe Head and Cranium.—Let us bear in mind the fact that the word head is used in speaking of a living person, and cranium, of a skeleton.
The science which makes a study of the cranium is called craniology. The cranium and the head may be studied either by observing the external form—cranioscopy or cephaloscopy; or else by taking measurements—craniometry or cephalometry. Craniology makes use equally of cranioscopy and of craniometry: in fact, if cranioscopy alone were used, certain anomalies might escape attention, because we can recognise them only by measuring the head; and conversely, if we confined ourselves to craniometric researches, we might miss certain anomalies of form, which we become aware of only by attentively observing the cranium. Frequently craniometry serves to verify cranioscopy. For example, a cranium may appear to the eye too large or too small, but certainly if we measure the cranial circumference with a tape-measure we shall have an accurate decision of a case which may well be a simple optical illusion. Indeed, we all know how easy it is to give an erroneous judgment, relying only on our senses; for the personal equation enters very largely into judgments of this sort. For instance, a person of low stature easily judges that other men are tall, and vice versa. To the eye of the Italian or the Frenchman, the hair of young English girls is a pale blond; to the Scandinavians of the North it is a warm blond. If two men possessed of different æsthetic tastes and in different frames of mind wish to describe one and the same garden they will give two widely different descriptions which will reveal far more of their individual impressions and moods than of the actual characteristics of the garden described. It is easy to understand how important it is in scientific descriptions to exclude completely the influence of the observer's personality. In the cranioscopic study of a cranium, for instance, the precise characteristics of that cranium are what must be found and nothing else whatever, no matter who the student is nor in what part of the world he is working. But in order to achieve this result it is not enough to take observations; it is also necessary to know how to observe, and in observing to follow a scientific method.
Cranioscopy.—Cranioscopic methods require that the skull shall be observed from several sides. Blumenbach, who studied crania by observing them from the vertex, divided them into ovoid, rhomboid, etc., while Camper, on the other hand, studying them in profile, classified them as flat, elongated, etc., and the conclusions of the two scientists were irreconcilable.
Fig. 146.—Facial norm.
Fig. 147.—Occipital norm.
Fig. 148.—Lateral norm.
The cranium must be observed from above, from the front, in profile and from the occipital part; and in such a manner that the observer's glance shall fall perpendicularly upon whichever cranial side is under observation. Hence it is said that the observation is made according to the norm, i.e., according to the perpendicular, and there are four norms in cranioscopy—vertical, frontal, lateral, and occipital. In this way we may be sure that no anomaly of form will escape the eye.
There are innumerable anomalies of form. We will indicate only the principal ones. In order to detect all the anomalies that may occur in a cranium it is necessary to observe it according to all the norms, each one of which may reveal a different set of anomalies.
A. Vertical Norm.—The word norm, as we have already said, has here the signification of perpendicular. To look at a cranium according to the vertical norm means to let our glance fall perpendicularly upon the vertex of the cranium. We may do this in one of two ways, either by raising our head above that of the subject of inspection, in such a way that our glance falls vertically upon it, or by bending back the head of the person to be observed until the crown of his head becomes perpendicular to our gaze. This norm is taken by placing oneself behind the person to be observed, who, if an adult, should be seated while the observer remains standing; and by taking the head to be examined between the two hands in such a way that the extended thumbs and index-fingers form a horizontal circlet around the cranial walls.
This is the most important of the norms, not only because it reveals the most important normal forms already described in the text, but also the greater number of anomalies such as are indicated below.
1. Crania with Rectilinear Perimeter.—It may happen that the line bounding the cranial vault is not curved but formed of broken straight lines from which various geometrical figures result, producing crania known as trigonocephalic, pentagonoid, parallelopipedoid, etc.
The most important among these and among all the abnormal forms is the trigonocephalic cranium, having the base of the triangle toward the occiput and the vertex toward the forehead. The result of such formation is that the frontal region is restricted, a circumstance of obvious gravity. The infantile cranium is normally pentagonoid; the persistence of this form in the adult is a sign of arrested development, but not serious. Sergi does not admit this form among the anomalies when the nodules are but slightly emphasised.
2. Asymmetrical and Plagiocephalic Crania.—The sagittal plane divides the cranium into two unequal halves. The asymmetry may be either frontal, in which case one frontal nodule is more prominent than the other—anterior plagiocephaly, or else parietal, in which case one of the parietal nodules is more prominent than the other—posterior plagiocephaly.
These are the two forms of simple plagiocephaly. It may happen that there is simultaneously an anterior and posterior asymmetry, and in such a case it generally happens that if the more prominent frontal nodule is on the right, the more prominent parietal nodule is on the left, so that the two more
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