Pedagogical Anthropology - Maria Montessori (best free novels TXT) 📗
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INCREASE IN WEIGHT OF BODY
According To Sutils
But these figures give no idea of the laws of growth that govern each separate organ, and that have been studied by Vierordt. According to this authority, the total weight of the body increases nineteen-fold from birth to complete development. Certain ductless glands, on the contrary, diminish in weight in the course of growth; the thymus, for instance, is reduced to half what it weighed originally.
Furthermore, the various organs all differ in such varying degrees, as compared with their respective weights at birth, that it facilitates comparison to reduce the weight of each separate organ to a scale of 1. On this basis we find that when complete development is attained, the eyes weigh 1.7; the brain 3.7; the medulla oblongata (spinal marrow) 7; the liver 13; the heart 15; the spleen 18; the intestines, stomach and lungs 20; the skeleton 26; the system of striped muscles 48.
And these widely different augmentations are not uniform in their progress, nor is the complete development of each organ attained at the same epoch. As a matter of fact, the brain acquires one-half its final weight at the end of the first year of age; the organs of vegetative life attain half their weight at the beginning of the period preceding puberty (eleventh year). To offset the lack of indications regarding such increases in weight, we have a guide in the morphology of growth, which reveals how differently the various parts of the body develop.
However empirical it may be from an analytical point of view, the datum of weight is a valuable index, and represents, taken by itself, a synthetic anthropological measure of prime importance.
It obeys certain laws of growth which are themselves of great interest; namely, there exist two periods of rapid growth: at birth and during puberty; while at various periods in childhood, between the ages of three and nine, there are alternations of greater and lesser growth analogous to those already noted in relation to stature.
Accordingly, the weight confirms the fact that the organism does not proceed uniformly in its evolution, but passes through crises of development during which the forces of the organism are all devoted to its rapid transformation; such periods represent epochs at which the organism is more predisposed to maladies, more subject to mortality and less capable of performing work (compare the observations already made in relation to stature).
Index of Weight.—Accordingly, weight and stature stand in a certain mutual relationship, but the correspondence between them is not perfect. In the study of individual physiological development it is necessary to know the anthropological relation between weight and stature; in other words, the ponderal index. Without this, we cannot get a true idea of the weight of an individual. For instance, if two persons have the same weight, 65 kilograms for example, and one of them has a stature of 1.85 metres and the other of 1.55 m.; it is evident that the first of these two will be very thin, because his weight is insufficient, while the second, on the contrary, will have an excessive weight.
A stout, robust child will weigh less, in an absolute sense, than an adult man who is extremely thin and emaciated; but relatively to the mass of his body, he will weigh more. Now this relative weight or index of weight, the ponderal index, gives us precisely this idea of relative embonpoint, of the more or less flourishing state of nutrition that any given individual is enjoying. Hence it is a relation of great physiological importance, especially when we are dealing with children.
The calculation of the ponderal index ought to be analogous to that of other indexes; what has to be found is its relation to the stature reduced to a scale of 100. In this case, however, we find ourselves facing a mathematical difficulty, because volumetric measurements are not comparable to linear measurements. Consequently it is necessary to reduce the measurement of weight by extracting its cube root, and to establish the following equation:
St:∛(W) = 100:X
whence
Pi = 100(∛(W))/S
The application of this formula necessitates a troublesomely complicated calculation, which it would be impracticable to work out in the case of a large number of subjects. But as it happens, tables of calculations in relation to the ponderal index already exist, thanks to the labours of Livi[35] and it remains only to consult them, as one would a table of logarithms, by finding the figure corresponding to the required stature, as indicated above in the horizontal line, and the weight as indicated in the vertical column.
Some authors have thought that they were greatly simplifying the relation between weight and stature by calculating the proportional weight of a single centimetre of stature and assuming that they had thus reduced the relation itself to a ratio based upon a single linear measurement (one centimetre), analogous to the ratio established by the reduction of the total stature to a scale of 100. But evidently such a calculation is based upon two fundamental errors, namely: first, no comparison is ever possible between a linear measure and a measure of volume; and secondly, the relation which we are trying to determine is that between synthetic measurements, i.e., measurements of the whole, and not of parts.
Fig. 37.
In the aforesaid method of computing (which is accepted by such weighty authorities as Godin and Niceforo), the number expressing the weight in grams is divided by the stature expressed in centimetres, and the quotient gives the average weight of one centimetre of stature expressed in grams. This method, which sounds plausible, may easily be proved to be fallacious, by the following illustration, given by Livi in his treatise already cited (Fig. 37). The two rectangles A and B represent longitudinal sections of two cylinders, which are supposed to represent respectively (in A) the body of a child so fat that he is as broad as he is long (the rectangle A is very nearly square), and (in B) that of a man of tall stature and so extremely thin that he very slightly surpasses the child in the dimensions of width and thickness (note the length and narrowness of rectangle B). Evidently the ponderal index of A is very high and that of B is very low. But if we calculate the proportional weight of one centimetre of stature, it will always be greater in the man than in the child, and consequently we obtain a relation contrary to that of the ponderal index.
Let us make still another counterproof by means of figures; let us take an adult with a stature of 1.70 metres and a weight of 19 kilograms; and a three-year-old child 0.90 m. tall and weighing 55 kg. (the normal weight of a child of four). In the case of the adult one centimetre of stature will weigh 65000/170 grams = 382 grams; while one centimetre of the child's height will weigh 15000/90 = 166 grams. In other words, one average centimetre of the child's stature weighs less than one centimetre of the adult, as it naturally should, while the ponderal index on the contrary is 23.6 in the case of the adult, and 27.4 in that of the child.
The reciprocal relations between stature and weight vary from year to year. In babyhood, the child is so plump that the fat forms the familiar dimpled "chubbiness," and Bichat's adipose "fat-pads" give the characteristic rotundity to the childish face; while the adult is much more slender. A new-born syphilitic child which, with a normal length of 50 centimetres, weighed only two kg.—and consequently would be extremely thin—would have the same identical ponderal index as an adult who, with a stature of 1.65 m., weighed 100 kg.
The evolution of the ponderal index forms a very essential part in the transformations of growth; and it shows interesting characteristics in relation to the different epochs in the life of the individual.
In this connection, Livi gives the following figures, for males and for females; from which it appears that at some periods of life we are stouter, and at others more slender; and that men and women do not have the same proportional relation between mass and stature.
Indices Indices Age in years Males Females Age in years Males Females 0 29.7 29.6 15 23.1 23.4 1 30.9 30.5 16 23.4 23.6 2 28.7 28.9 17 23.1 23.7 3 27.5 27.3 18 23.2 24.1 4 26.5 26.6 19 23.4 24.1 5 25.8 25.6 20 23.5 24.1 6 25.1 24.8 — — — 7 24.4 24.1 25 23.7 24.1 8 24.0 23.8 30 23.8 24.1 9 23.5 23.5 40 23.9 24.7 10 23.1 23.2 50 24.3 25.3 11 22.8 23.3 60 24.6 25.3 12 23.1 23.6 70 24.5 24.9 13 23.4 23.5 80 24.4 24.7 14 23.1 23.3 — — —It may be said in general, so far as regards the age, that the following is the established law of individual evolution: during the first year the ponderal index increases, after which it diminishes up to the period immediately preceding puberty (eleventh year for males, tenth year for females), the period at which boys and girls are exceedingly slender. After this, throughout the entire period of puberty, the ponderal index seems to remain remarkably constant, oscillating around a fixed figure. At the close of this period (seventeenth year for males, fourteenth for females), the ponderal index resumes its upward course (corresponding to the period in which the transverse dimensions of the skeleton increase, and in which the individual, as the phrase goes, fills out), and it continues to rise well into mature life (the individual takes on flesh); until in old age, the ponderal index begins to fall again (the soft tissues shrink, the cartilages ossify, the whole person is shrunken and wasted.)
Fig. 38.
Women, during their younger years are on a par with men in respect to the ponderal index, but in later life surpass them, because of woman's greater tendency toward embonpoint, since she is naturally stouter and plumper than man, who is correspondingly leaner and more wiry.
The following diagram indicates the progressive evolution and involution of the ponderal index throughout the successive stages of life:
The ponderal index has revealed certain physiological conditions in pupils that are extremely interesting. Some authors had already noted that the ponderal index was higher in well-nourished children (Binet, Niceforo, Montessori); but last year one of my own students, Signorina Massa, in a noteworthy study of children, all taken from the same social class and quite poor, and who did not attend the school refectory or have the advantage of any other physiological assistance, established the fact that the more studious children, the prize winners, have a lower ponderal index and a muscular force inferior to that of the non-studious (negligent) pupils. That the development of the ponderal index stands in some relation to the muscular force, might already have been deduced from the fact that the greatest increase of weight is due, in the evolution of the individual, to the system of striped muscles. Studious children, accordingly, are sufferers from denutrition through cerebral consumption; furthermore, they are weakened throughout their whole organism; in fact, I discovered, in the course of researches made among the pupils in the elementary schools of Rome, that the studious children, those who received prizes, had a scantier chest measurement than the non-studious. This goes to prove that school prizes are given at the cost of a useless holocaust of the physiological forces of the younger generations!
That the ponderal index has an eminently physiological significance, is further shown by the following comparative figures between normal and weak-minded children. The stature, which is biologically significant, is lower in the weak-minded; but their ponderal index is greater when they are well fed, as in the asylums in Paris.
Accordingly, the sole cause of the physical inferiority of studious children is study, cerebral fatigue.
BIO-PHYSIOLOGICAL DIFFERENCES BETWEEN NORMAL AND WEAK-MINDED CHILDREN
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