Pedagogical Anthropology, Maria Montessori [online e book reader TXT] 📗
- Author: Maria Montessori
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Plagiocephaly is extremely common; if very apparent, it constitutes a grave defect, but not if only slight. For that matter, it would be difficult to find a cranium rigorously symmetrical, even among normal persons.
3. Crania with curved and symmetrical lines, but in which the perimeter consists not of a single ellipsoidal curve, but of two curves.
a. Clinocephalic Cranium.—The coronal suture has a girdle-like furrow, in such fashion that there result an anterior and a posterior curve which together form a sort of figure 8. This anomaly may be perceived also from the lateral norm.
b. Cymbocephalic Cranium.—- There is a girdle-like furrow along the sagittal line, so that the cranium has the appearance of being divided into two pockets, one on the right hand and the other on the left.
B. Lateral Norm.—The observer must stand at the side of the subject to be observed and look at him perpendicularly to the profile.
We remain standing while we look if the subject is an adult and is standing up, but we sit down if the subject is a child and is standing; and we determine the vertical position by moving the subject's head as the occasion requires.
I note, as seen from this norm, two anomalies in which the ellipsoidal uniformity outlining the profile of the cranium is altered.
a. Oxycephalic Cranium.—The line of the profile is noticeably raised at the bregma, from which the anterior part of the cranium continues to rise, almost in the direction of the forehead, instead of curving backward. In its entirety this anomalous cranium has the form of a "sugar loaf."
b. Acrocephalic Cranium.—The line of the profile, on the contrary, is not raised until near the lambda.
C. Occipital Norm.—The observer places himself behind the subject and gazes perpendicularly at the occipital point.
D. Frontal Norm.—The observer stands in front of the subject and gazes at him on a level with the forehead.
I may point out only one very important anomaly seen from this norm.
a. Scaphocephalic Cranium.—The lateral parts of the cranium are flattened to such a degree that the vault is extremely narrow along the sagittal line (see Figs. 51 and 52).
Craniometry.—The volume of the cranium is of high importance because it bears a relation to that of the brain. In the studies which have been made relative to the correspondence between physical and intellectual development, the measurement of the cranial volume comes first in order.
In measuring the cranium it is necessary to use:
a. the millimetric tape measure, b. the craniometric calipers, c. the compass with sliding branches, d. the double square. In order to facilitate the task of measuring and to secure uniformity it is necessary first to locate the craniometric points to which it will be necessary to apply the instrument. These craniometric points are easily located on the cranium, where a great number of them have been studied. In the case of a living person, on the contrary, these points are reduced to a small number because of the difficulty of accurately locating them.
The points on the vault of the cranium, along the sagittal line, are:
The nasion (point of union of the nasal and frontal bones). The ophryon (middle point of the line tangent to the two superciliary arches, a line corresponding to the horizontal drawn transversely across the forehead and passing through the two points on the temporal lines which are nearest to the median line. This point lies in an important region of the forehead, situated between the two eyebrows—the glabella. The central point of the middle region of the forehead above the glabella is called the metopion). The bregma (point of juncture between the coronal and sagittal suture). The vertex. The lambda (point of juncture between the sagittal suture and the occipital or lambdoid suture). The occipital point. The inion (situated at a level midway between the occipital point and the occipital foramen).Laterally we have these other craniometric points:
The external orbital apophysis (formed from the frontal bone). The supra-auricular point. The auricular point (corresponding to a little depression which may be felt just below the tragus and in correspondence with the zygomatic arches). The minimum frontal point (a bony angle which may be felt about 1 centimetre above the external orbital apophysis, along the temporal line).On a living person the following points can easily be located:
Along the sagittal line:
The nasion. The ophryon. The vertex. The occipital point.Laterally:
The external orbital apophysis. The supra-auricular point. The auricular point. The minimum frontal point.Now, with these points as guides it becomes practical to measure the various curves and diameters of the cranium. The curves are measured by means of the millimetric tape; the diameters by means of the calipers.
There are various curves; we shall confine ourselves to considering only the following:
The maximum circumference, which is obtained by passing the tape across the ophryon, the occipital points and the supra-auricular points, beginning to apply it at the ophryon. Its measure varies from 520 to 540 mm. in man and from 490 to 510 mm. in woman, if taken from the skull. In the case of a living person 20 mm. should be added.
If we find a circumference greater than normal, we are beginning to enter upon the anomaly which goes by the name of macrocephaly. If, on the other hand, the maximum circumference is notably smaller, we are entering upon the anomaly of microcephaly.
Measurement of Diameters.—Maximum Antero-posterior Diameter.—With the left hand place one branch of the calipers upon the glabella; the other extreme point is to be sought tentatively along a vertical line dividing the occiput in two halves. Partially close the calipers by means of the screw and then make trial by raising and lowering the posterior branch. It ought to move with a slight friction.
This is the classic diameter which measures the maximum length of the cranium and which, as we have seen, it is customary to compare with the width in order to obtain the cephalic index. In the adult man it normally oscillates between 170 and 180 mm.
Fig. 149.—Inspecting cranium (lateral and vertical norms).
Maximum Transverse Diameter.—This measures the width of the cranium. The investigator places himself in front of the subject in order to keep the compass quite horizontal through the guidance of the eyes. The maximum distance is found by experimenting. It normally corresponds very nearly to the supra-auricular points. In children this diameter is frequently situated higher up toward the parietal nodules; in men of tall stature, in whom the cranial vault is generally slightly developed, this diameter may be found, on the contrary, lower down, near the mastoid apophyses. If this diameter occurs similarly low down in children, a notable growth in stature may be prophesied (Manouvrier); and if inquiry is made it will be found that the parents are very tall. This diameter measures, in the adult, from 140 to 150 mm.
Vertical Diameter.—This measures the height of the cranium from the occipital foramen to the bregma. This diameter cannot be measured directly excepting on a skull; in the case of a living person its projection is taken, which, though far from accurate, is given by the distance between the vertex and the external auditory meatus.
It is necessary to use the double square. The horizontal branch is placed tangent to the vertex, its direction should be perceptibly parallel to the transverse orbital line, the graduated vertical branch should pass over the auricular foramen. The required number may be read, corresponding to the point of the tragus.
The height of the cranium is exceedingly important; its variations produce variations in the physiognomy.
In the first period of childhood, the cranium is very low in comparison to its width; this is also true of dwarfs. In these cases the width of the cranial vault is large in comparison to that of the base; a low cranium bulging above is distinctive of babies and dwarfs.
In the adult this diameter measures from 130 to 140 mm.
Among the other measurements which an taken on the cranium, the following may be cited:
The antero-posterior metopic diameter: from the metopic to the occipital point. In children it is sometimes the maximum longitudinal diameter.
The ophryo-iniac diameter from the ophryon to the inion.
The minimum frontal diameter: between the two minimum frontal points.
The maximum frontal diameter: between the two external orbital apophyses.
The bistephanic diameter: between the two stephanic points.
The bitemporal diameter: this is the greatest width of the cranium between the verticals passing through the base of the tragus.
The biauricular diameter: the craniometrical points are in front of, and a little below, but very near to the upper insertion of the auricle. They are little depressions that can be felt, as we have already said, by applying the finger along the upper edge of the root of the zygomatic arch.
Height of forehead: from the ophryon to the roots of the hair.
Circumferences and Curves:
Anterior Semicircle.—The tape is applied from one supra-auricular point to the other, passing through the ophryon; it corresponds to the anterior part of the maximum circumference. Manouvrier measures it in correspondence to the verticals erected from the tragus.
Posterior Semicircle.—This is obtained by subtracting the anterior semicircle from the whole circumference.
Vertical Curve of the Head.—The tape passes through a plane that is vertical to the orientated head, starting from the supra-auricular points or from the tragus, according to different authorities.
Cephalic Index.—This is the proportion between the maximum transverse and longitudinal diameters. It is obtained by applying the familiar formula:
Ci = (100×d)/(D)
in which d represents the transverse diameter and D the longitudinal. The index represents the percentual relation between the two diameters, and is obtained from the formula by reducing the greater diameter to a scale of 100, as follows:
D:100 = d:X, whence X = 100×d/D
Instead of working out the calculations, we may find the required index in the tables already compiled.
Volume.—The volume of the cranium cannot be taken directly, except in the case of a skull. After the various osseous foramina have been closed, the cranial cavity is filled through the occipital foramen with any one of a number of substances (millet, shot, water, etc.), which is afterward measured. The method of taking this measurement is practised on a facsimile of a cranium already calculated, and usually made of metal.
But in the case of a living person the direct calculation of the volume is impossible. Nevertheless various empirical methods have been sought for obtaining this measurement, even though imperfect and approximate. Recently renewed use has been made, especially in France, of an approximate calculation made by means of Broca's cubic index. The volume of the cranium is equal to half the product of the three diameters, divided by an index which varies according to age.
This index is as follows:
Adults from 25 years upward. men 1.20 women 1.15 Young persons from 25 to 20 years. men 1.15 women 1.10 Young persons from 20 to 16 years. men 1.10 women 1.08 Children of both sexes. 15-10 years 1.07 10-5 years 1.06 5 years and below 1.05An index of cranial development is afforded by the maximum circumference. The average volume of the normal adult cranium is about 1,500 cubic centimetres: mesocephalic cranium.
When the cranium is much inferior in volume, it is called microcephalic (from 1,200 down to 700 cubic centimetres). When on the contrary it is much superior (from 1,900 up to 2,200 cubic centimetres), it is called macrocephalic or megalocephalic.
For the face, the following craniometric points should be noted:
Along a longitudinal line:
The nasion (point of meeting of the nasal and frontal bones). Subnasal point (meeting of nasal septum with upper maxilla). Upper alveolar point (between the two upper incisors at their point of insertion). Lower alveolar point (point corresponding to the above, in the lower maxilla). Mental point (middle point of the chin). The following craniometric points are situated laterally. Auricular point (corresponding to the auricular foramen; in living persons it is situated on the tragus). Malar point (on the malar bones). Zygomatic point (corresponding to the zygomatic arches). Gonion or goniac point (angle of mandible).The face also may be studied by inspection—prosoposcopy; and by
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