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During the last few decades a vast amount of anthropometrical material has been collected. By far the greatest part of this material and the most valuable has been collected by the directors of gymnasia connected with colleges, schools, and associations of young people, so that the average anthropometric type of the young American may be said to be fairly well known.

The material has been collected largely from a practical point of view. The main object of the measurements is to determine how the physical development of a given individual compares with the average physical development of the group to which he belongs. The observed deficiencies in his development determine the selection of gymnastic exercises by which the physical development of the subject may be improved. The application of anthropometry to practical work in the gymnasium is founded on two fundamental assumptions: First, that the average measurement represents an ideal type; and, secondly, that small variations from the type may be considered as physiological variations. I wish to discuss these two fundamental assumptions in some detail.

It has often been pointed out that the average type obtained by a series of anthropometrical examinations includes not only those individuals who are perfectly healthy and normally developed, but also others who are deficient in one or the other respect. If abnormality had an equal tendency to increase or to decrease the normal measurement, this cause of variation might be disregarded. It would seem, however, that most of the causes of abnormalities bring about a retardation of development with the result of a final diminution of the value of the measurement. Malnutrition causes decrease of stature. Deficient development of the lungs results in small thoracic circumference and capacity. Disuse of muscles results in lacking development of muscular parts. We may therefore conclude that the types, as obtained from miscellaneous measurements, represent a somewhat pathological type, not by any means the ideal that would be observed if the type were constructed from measurements of individuals of absolutely perfect health record. Since the general sanitary conditions improve with increasing wealth, it is probably safe to assume that the differences observed between the physical development of the poor and those of the wealthier portions of our communities are due largely to the elimination of unfavorable influences.

From this point of view it would seem desirable to subdivide the subjects measured in a number of classes according to their health records. Such classification must be founded partly on the history of each case, partly on the observations of the gymnasium director. The metrical results obtained from the best class would be most likely to give us an insight into the form of the normal individual. As defined in this way, the normal individual would not be the one whose form is the most frequent, but the one whose form would be most frequent if conditions were as favorable as possible during the period of development.

A second important question which arises in this connection is whether it is justifiable to assume that there is one and only one ideal type, which all the individuals of our community approach. If different classes of our community represent different types, it would evidently be incorrect to measure the abnormality of an individual by comparison with one single ideal type.

As a matter of fact the individuals measured in our gymnasia differ in regard to their ages, their descent, and the environments in which they live, and it is necessary to decide whether it is justifiable to disregard all these influences. Our American population embraces descendants of practically all European nationalities, and, therefore, includes representatives of all the different types inhabiting Europe. Speaking in a general way we may say that we must distinguish at least three types among the European populations: the blond, tall, long-headed type of Northern Europe; the dark, tall, short-headed type of Central Europe; and the short, dark, long-headed type of Southern Europe. These three types must have been distinct for exceedingly long periods, and possibly the present distribution of European types may be considered as a resultant of their intermixture. I do not mean to say that the three types enumerated here are the only fundamental European types. The views of anthropologists on this point vary to a certain extent, but it is sufficient for our purpose to recognize that in our population the three types enumerated here are represented with a rather strong preponderance of the North European type.

If we happen to measure an individual belonging to the Central European type, we must compare his measurements with the ideal Central European type. It would, evidently, be wrong to compare him with the standard obtained from measurements of North Europeans. For this reason the method of judging the physical development of an individual belonging to a population of mixed descent by comparing him to the general type does not seem free of objection.

The same is true in regard to the effect of age, which factor becomes of the greatest importance in work among growing children. When we measure a sixteen-year-old boy we are by no means certain how near the particular boy is to the adult stage, how nearly he has completed his development. The most superficial examination of the physical and mental development of children and of adults brings out the fact that the physiological development of the individual cannot be measured by years only. We observe children who are precocious; who are in every respect in advance of their age. We observe others who are physically and mentally retarded; while later on the same children will overtake those who previously were far ahead of them. The same phenomenon may be observed when we compare the physical development of older people. With some, the period of decadence begins before the fortieth year is reached, while others retain their full vigor until much later times. The distinct signs of old age also appear in different individuals at widely differing times. It is, therefore, evident that the whole current of life must not be measured by years alone, and that individuals vary, if we may use the expression, in regard to the tempo with which they run through their life’s course.

This way of considering the phenomena of growth, development and decay gives a sufficient explanation of all the peculiarities observed in anthropometrical statistics of children, and for this reason I regard this mode of considering the course of human life as fully consistent with observation.

Bearing in view this fact, it is evidently not sufficient to classify individuals according to their ages, but we must also bear in mind the acceleration and retardation of individual development.

But, it may be asked, how is it possible to determine in each and every case the type with which the individual must be classed, and the period of development which he represents?

It would seem that at the present time neither of these questions can be definitely answered. The correlations of the series of measurements characterizing the various European types have never been determined, and the correlations characteristic of various periods of development are also unknown. It would therefore, in the present stage of our knowledge, be largely a matter of judgment on the part of the gymnasium director how to classify each individual according to his general characteristics; or it would be necessary to establish a number of tentative classes in which the individuals might be arranged.

It appears, however, from these considerations, that it is highly desirable to subdivide the anthropometrical material collected in gymnasia in a most minute and painstaking way in order to investigate in how far it will be feasible to class any individual with a definite type. I do not wish to convey the impression that I consider it feasible even after the most extended statistical investigation of anthropometrical material to establish a number of clearly distinct types, the variability of each of which would be so small as to allow us to class any individual with a definite type. I only desire to point out the necessity of classifying our material from various points of view, and of placing each individual in the class to which he most probably belongs.

A diversity of types manifests itself in a series of measurements. It is one of the fundamental laws of correlation that in a homogeneous series deviations from any typical measurement are proportionate to the excess or deficiency of any other measurement. Taking, for instance, stature as a standard, the following condition would be found: If one man is, let us say, ten centimeters in excess of the ordinary stature, another man twenty centimeters in excess of the ordinary stature, then the excess of chest circumference of the second man will be twice as large as the excess of chest circumference of the first man. If, however, the tall individuals should happen to belong to a type different from that to which the majority of short individuals belong, then this law would no longer hold good. We have, therefore, a means of discovering in our extensive anthropometrical series a mixture of divergent types. This investigation is an important one and should be taken up at an early date.

I wish to bring to your attention another point which seems to me of vital importance. We are accustomed to consider the types represented in our tables as constant. We speak, for instance, of the typical measurements of an entering class, and of those of a graduating class. There is a change in the values obtained from these two classes. This change is due to a gradual development. Our point of view is, therefore, only a rough approximation to the actual conditions. The anthropometrical problem is not a statical one, but a dynamical one, and we should take into consideration the rates of changes characteristic of various individuals and their effect upon the distribution of measurements. If we include this problem in our plan of researches it becomes vastly more complex, but at the same time vastly more interesting, because the physiological changes in the individual and the types and variabilities of these changes become accessible to investigation.

For these purposes we need repeated measurements of the same individuals. We must not confine ourselves to comparisons of general anthropometric tables, but we must compare individual measurements with individual increments. The study is still in its infancy, but its importance is far-reaching. It makes it incumbent on our observers to use the most painstaking care in their measurements, and to avoid all rounding off. The increments are in most cases so small that errors introduced by the process of rounding off may be larger than the values which must be investigated. If, for instance, measurements of statures of boys of 16 or 17 years are made, it will be seen that the small average increase may be completely obscured by the inaccuracy of measurement and by the process of rounding off to the nearest full or even half centimeter. If we wish to make progress in this important branch of our inquiry, the very highest accuracy of method of measurement must be demanded.

It is important to bear in mind that questions of this character are not merely of theoretical value, but will also lead to a new point of view in the practical application of anthropometrical results.

The second question which I desire to discuss relates to the scope of physiological variation. We know that no two organisms are absolutely alike, and that various processes lead to slight differences of form in different individuals belonging to the same type. It is only when these variations assume excessive values that we are justified in speaking of pathological cases in so far as the combination of measurements observed is a rare one, and therefore likely to be due to abnormal causes. What, then, is the range of physiological variation? When we are dealing with single measurements we may, perhaps, assume that all those individuals are normal which represent the middle half of the total series of measurements. The lowest measurements and the highest measurements, both of which combined constitute the other half of the series, might be considered as abnormal. When we consider two measurements of the same individual, the question becomes somewhat more complicated. If the two measurements are not correlated at all, if the one changes without influencing in the least the other, we might say again that that series is normal which embraces the middle half of the two measurements. Evidently we should measure the normality or abnormality of a certain combination by the frequency of its occurrence. The average type in regard to both measurements will be the most frequent one, and slight deviations in both directions will have comparatively high probabilities. In the particular case which we are discussing here, namely, when both measurements are entirely independent of each other, it is evident that an individual who has a small deviation in one respect and no deviation at all in regard to the second measurement, will be more frequent than an individual who stands, as we are accustomed to say, in both respects on the same percentile grade. Supposing that stature and transversal diameter of the head were entirely independent of each other, it would be more probable to find a tall man with the average transversal diameter of the head than a tall man with a correspondingly large transversal diameter of the head.

As a matter of fact, there are hardly two measurements that do not influence each other to a certain extent. This fact is easily seen when we tabulate the measurements of tall people and of short people. It will be found that on the whole the measurements of tall people are larger than those of short people, although the proportional increase of the average measurement is not the same for all measures. In all these cases that combination is most probable for which the second measurement bears a certain characteristic relation to the first measurement, which is determined by what we call the coefficient of regression.

It appears from these considerations that a type which is characterized by a series of measurements, all of which represent the same percentile grade, and which, on our anthropometrical charts, would be represented by a number of points standing very nearly on the same level, is not as probable as a type which in one of its measurements deviates considerably from the average type, while in all other respects it has only a comparatively small deviation from the average type. This considerable deviation may occur in any of the numerous measurements which we are in the habit of taking. And for many combinations of deviations, one of which is large while the others are small, the frequency of the type will remain the same. We find, therefore, as a result of these considerations, that the most frequent types, and for this reason the types which we must consider as inside the limits of physiological variations, are not by any means those which in all respects are enlarged or reduced replicas of the average type, but such that deviate more or less from this type in regard to their correlated measurements.

I have tried to point out in these remarks a few directions in which it would seem that our anthropometrical material may be made more useful and more significant than it is at the present time. I am fully aware of the difficulties and of the vast amount of labor involved in carrying out any of the suggestions here outlined, but I fully believe that any labor devoted to this matter will be repaid by results interesting from a scientific point of view and valuable for the gymnasium director. Much can be attained by hearty co-operation, and I hope that our deliberations may lead to a way of making the vast amount of anthropometric work that we are doing more useful in scientific and practical lines.

[104]

American Physical Education Review, vol. 4 (1902).