Fourth: It is well to remember that from a larger bio- logical view, every higher animal is not only composed of organs phyletically old and new, but that the order of their development may even be changed. Basal and lapidary as is the great biogenic law that the individual recapitulates the growth stages of his race, the work of Appel, Keibel, Meh- nert,^ and many others has demonstrated abundant inver- sions of it. The heart, e. g., in the individual develops be- fore the blood-vessels, but this reverses the phylogenetic order. The walls of the large vessels develop before the blood- corpuscles, while the converse was true in the development of the species. Ontogenetic age in all such cases is an index only of the intensity of cenogenetic energy. Retarded devel- opment of an organ, on the other hand, is an indication of regressivity, and many writers have collected cases showing * See especially his Biomechanik. Jena, 1898.
56 THE PSYCHOLOGY OF ADOLESCENCE that abbreviation and retardation of the different organs of a creature which is their bearer are ontogenetic processes that are constantly operative. The latter may affect the date of the first appearance of an organ, the differentiation of its tissues among each other, or the entire processes of growth of a part or all of them. Organs are progressive according to the degree of their vitaHty. The rapidity of the growth of a part is directly as the degree of development acquired by the phyletic process. Owing to this heterochrony, every ani- mal, man included, is a mixture of high and low, new and old qualities, so that in certain respects not a few animals excel man, and we are slowly gaining and slowly losing traits. In general, we may say with Jordan that *' if the history of an individual is an epitome of the history of the group to which the individual belongs, then adaptive characters appearing late in the growth of the individual must have appeared late in the history of the group." ^ But this is only a part of the fact, for as Hyatt ^ states the matter, " all modifications and variations in progressive series tend to appear first in the adolescent or adult stages of growth, and then to be inherited in successive descendants at earlier and earlier stages according to the law of acceleration, until they either become em- bryonic or are crowded out of the organization and replaced in the development by characteristics of later origin." Cope ^ has modified this law by suggesting that '' the accelerations in the assumption of a character progressing more rapidly than the same in another character must soon produce a type whose stages were once the exact parallel of a perma- nent lower form; the condition of inexact parallelism." Hence he infers that acceleration has occurred in some traits and qualities, but also that, as each type has had its time of culminating perfection, retrogression and retardation have also occurred, till some characters have been lost. Thus in on- togeny or the development of the individual, we often have characters that occurred simultaneously in the ancestral or- ganism appearing successively. Indeed, many variations of parts and functions, both those of excess and defect, may * Smithsonian Contributions, No. 673, Preface, p. ix.
• Origin of the Fittest, p. 142.
PARTS AND ORGANS DURING ADOLESCENCE 57 have a morbid origin. Virchow, describing the differences between diathesis, Anlage, and variations, makes the former permanent, but holds that the latter especially may arise from a pathological inception.^ Weisbach ^ thinks, e. g., that the measurements of sav- ages show that ape-like traits are not concentrated in any race, but are scattered among different races, and that some are found even among Europeans. Turner^ infers that no one race is inferior or superior to all others in all traits. He finds, e. g., that while the Lapps and Eskimos most approach apes in the proportions of thigh to upper arm and of shaft of lower to upper limb, they are among all races one of the most widely removed from apes in the no less important ratio of forearm to upper arm and of leg to thigh. In other re- spects, the Fuegians are among the most ape-like of men, yet in pelvis and sacrum they rank high. While on the whole, in the important skeletal character of skull and pelvis, the Europeans are more removed from the general type of mam- mals, it is by no means as yet proved that the higher races have been derived by graded perfection of all structure from the black or any other existing race or from the Simian type. In some respects the so-called low races are more developed out of and even opposite to the pithecoid type than are the most civilized.
Fifth: In the present state of the question between pre- formation and epigenesis we shall assume that the earlier stages of life are more conformable to Weismannism, and the later to the views of Hertwig. The eozooic or paleoatavistic bases of heredity are the formative principles of fundamental organs, condition all others, and are constant and more inde- pendent of recent environment both in the time and degree of their development. But even if we assume the monophyletic origin of animal life^ it will still follow that as maturity and on the whole death are longer delayed as we ascend the scale of being, more and more weight must be assigned to those qualities which are later acquired than to those which are * Verh. Acad. Wiss. Berlin, 1896.
' Reise der Novara. Anthropol. Theil. 1867, p. 26g.
' Voyage of the M. S. Challenger. Zool., vol. xvi. Bones of the Human Skeleton.
58 THE PSYCHOLOGY OF ADOLESCENCE earlier and more stable. Even if we admit that the rudiments of all the chief characteristics possessed by the species lie dormant in the egg, this does not compel us to infer that there is no inherited congenital indefiniteness, to say that all is predetermined, that there are no latent energies to be not only set off but guided by stimulation, or that the only limitation, to the opening of new lines in all directions, pre- viously fixed in the constitution of germ-plasm is that by devel- oping some modes of reaction, certain others become impos- sible. All we need to assume is that there are neoatavistic factors, and that the later part of each individual life is more characterized by the evolution of acquired qualities. Promi- nent among the epigenetic elements are the effects of use, which increase from birth onward, while organs not needed tend to atrophy or become rudimentary as their functions cease. Not only the relations between these two functions, but recent biological discussions repeat, in many respects, those which Locke inaugurated concerning innate ideas, and the issue of the two discussions is also analogous. Each of these principles will have abundant illustrations in this chapter.
A. The Growth of the Bones. — To secrete solid sub- stances is one of the primitive powers of animal organisms, as is seen in all of the siliceous and calcareous shell- made oozes (pteripod, globigerina, radiolarian, diatome, etc.) that cover so deeply the primitive ocean-bed upon which they are always snowing down, in the form of coral formations, molluscan shells, Crustacea, articulata, the bony coats of insects, the carapaces of exoskeletal mammals, etc. Although this tegumentary framework is now represented in man only by hair, nails, and perhaps the dermal bones of the head and secon- dary or outer skull, suggestions and recrudescences of it are still often seen in abnormal and monstrous individuals, not only in defects of the endoskeleton, but in various forms of outer callosity In vertebrates, the axial system is both ontogenetically and phylogenetically first to appear, and can be detected within the first month of fetal life. The development of the appendicular system of limbs of all kinds, first in the membranous and then in the bony stage, is later very grad- PARTS AND ORGANS DURING ADOLESCENCE 59 ual., and in general proceeds from the larger to the smaller bones, and from the central or fundamental to the distal or accessory part, the limb-fingers, toes, etc., coming after arm and leg bones. Here, too, the force of heredity is stronger and truer in the early stages, so that congenital de- formities and insufficiency are more liable for the parts that develop late than for those that develop earlier. This general law, however, has frequent exceptions. The skull, as we go up the vertebrate scale, has grown at the expense of the cervical vertebrae, and strangely, the first bone in the embryo to ossify is commonly the clavicle, which has so important a function in expanding the shoulders in the erect position, frees the arms from locomotive functions, and gives them a power and range of lateral movement almost equal to that in the mesial plane.
Just before and after puberty there is a great increase in the growth of bones, and at the close of the adolescent ferment the skeleton is considerably extended and also much consolidated and joined together. This growth is much accentuated in the larger and especially in the longer bones, which have been chiefly measured. Kotelmann, Hall, and Moon have shown that they grow in thickness as well as in length, adding new periosteal layers. The motor apparatus in men, consisting of 223 bones and about 316 muscles, con- stitute by weight some -^-^ of the adult body, so that its increase is the chief factor of growth. Augmenting twenty-six fold from birth to maturity, the weight of the skeleton varies, with no yet fully determined law, from thirteen to twenty- three per cent that of the body, declining both relatively and absolutely in old age.^ For the prepubertal stages of growth it is still impossible to give exact data. Miihlmann ^ can find but ' Ueber die Ursache des Alters. Wiesbaden, 1900, p. 150.
6o THE PSYCHOLOGY OF ADOLESCENCE six careful attempts to weigh the skeleton at different ages, and from these constructs the table for males on page 59.
In the following cut, for which I am indebted to my colleagvic Professor Sanford, the skeleton of an infant is mag- nified to the approximate length of that of an adult, to show C B A a, skeleton of an adult: b, skeleton of a new born infant on the same scale; r, the same infant's skeleton magnified photographically to approximate the length of the adult skeleton, how monstrous maturity would be if the bones grew in equal proportions in all their dimensions. The skull and face w^ould be enormous, the neck long, the shoulders low or almost absent, the thorax narrow laterally but deep from front to back like a quadruped, the arms and especially the legs short, the hips small and feeble, etc.
PARTS AND ORGANS DURING ADOLESCENCE 6l (a) Sitting and Standing Height. — Important and interest- ing is the relation between the growth of the upper and lower lengths of the body, or the trunk from the vertex to the hip, as compared with that of the leg. Unfortunately, there have been discrepancies in taking these measurements, so that results are as yet unsatisfactory. Zeissing ^ found individual differences here so great that the proportions of some chil- dren at four were like those of others at fourteen, while Liharzik thought this ratio so distinct for each period of Hfe and so uniform for all that he could approximately determine the age by it alone. Landsberger ^ measured this relation only from the age of six to that of twelve years, and found the percentage of lower length to increase from 56.1 to 59.3 per cent of the entire length of the body.
While the middle of the body by length slowly descends with growth, the center of gravity descends relatively with growth, but ascends absolutely, and in the adult male is in the pelvis just above the hip-joint.^ Weber found the center of gravity in a male body 166.92 centimeters long, to lie 8.77 cen- timeters above the axis of rotation of the head of the femur; 0.87 centimeter above the promontorium; 94.77 centimeters above the heel; 72.15 centimeters below the sinciput. Accord- ing to Vierordt,* if the body were divided at the level of the crista of the ischium (the lower part of the hip-bone) and the total be divided into 1,000 parts — Liharzik, who divided a little lower at the pubic symphi- sis, found that — W. S. Hall ^ found that at nine years the height of the pubes was exactly equal to that of the body, and at twenty- * Vierordt. Physiol, des Kindesalters, p. 267.
' Das Wachsthum ins Alter der Schulpflicht, p. 245.
' Ueber den Schwerpunkt des menschlichen KSrpers. W. Braune u. O. Fischer. Leipzig, 1889.
62 THE PSYCHOLOGY OF ADOLESCENCE three, when the middle of the body had moved down to that of the symphysis, it was fifty-one per cent.
Moon ^ concluded that at fifteen the limbs are relatively longer in proportion to the body than those of the man or the boy of eleven. In sitting height, or the length of the vertebral column, there is a retarded stage of growth relative to height during the entire period from eleven to fifteen. Later ^ he found that growth of sitting height was independent of the approach of puberty. This increases for a year or two before as well as afterward. In fine, the legs tend to outstrip the other components of height during early youth, but afterward increase more slowly; while the sitting height increases rapidly.
Bowditch ^ says " women appear to be relatively longer in body and shorter in the legs than men." By measuring 1,546 girls and 324 men, mostly college and normal students, he found the average sitting height to be 53.24 per cent of the total height without shoes. Sargent has made this a trifle less, viz., 52.7 per cent. Ranke * takes the relatively greater body length of woman for granted and infers that she is thus embryologically lower than man, and Huxley states that long thigh and forearm are distinctively human traits. Hitch- cock,^ however, compared measurements of 500 students each of Amherst (male) and Mount Holyoke and Wellesley (fe- male), where the average age of entrance is nineteen, and found that while each sex had about 1.9 pound weight for every inch in height, and that while the females excelled a trifle in length of head and neck, the males were seven per cent taller and the male trunk was eleven per cent longer than that of the female, and that even the distance from pubis to navel was twelve per cent longer in the male. This surprising result, so con- trary to the common opinion that the female trunk is rela- * The Growth of Boys. Proc. Am. Ass'n for Advancement of Phys. Education, « The Question of Growth at Puberty. Am. Phys. Ed. Rev., Sept., 1899.
* Beitrage zur Anthropol., p. 490. Miinich, 1883.
^ Comparative Study of Measurements of Male and Female Students at Amherst, Mount Holyoke, and Wellesley Colleges. Journal of Physical Education, PARTS AND ORGANS DURING ADOLESCENCE 63 tively the longest, can not yet be interpreted. It is possible that these girls are not average representatives of their sex, but more mannish. There is some reason to believe that relatively long-bodied women are higher and better mothers and that relatively long-limbed girls are decadent, as we shall see later.
Dr. G. M. West ^ concluded from the measurements of 3,250 Worcester school children that girls' sitting height began to rise rapidly at twelve, before which age it had been very slight, and rose for two years. From the fifteenth to seventeenth year inclusive, the growth of boys rises, but drops the next year. His curves suggest that up to the twelfth year in girls, and to the fifteenth year in boys, a large part of the growth in stature is made in the lower limbs, while after these ages it is made largely in the trunk. During all the period from five to eighteen the limbs of boys grow more rapidly than the trunk, while with girls, the period of greater comparative growth is divided about equally between the extremities and the trunk. The trunk is relatively longer in girls than in boys, except from the seventh to the tenth year, while after the thirteenth year, girls' bodies are relatively still longer. After the twelfth year the annual increase in sit- ting height is less than before, though boys maintain a more uniform rate during all the period of acceleration; while both sexes make greater annual growth after than before twelve, yet girls make the greatest absolute increase before, and boys after that period.
Porter ^ concluded from his measurements on 33,500 children that sitting height in girls attained its fastest rate of growth at thirteen and in boys at fifteen, and that the period during which girls exceed boys in size is longest in sitting height. Hrdlicka ^ found that the greatest length of lower limb in the sexes taken together was attained from the thirteenth to the sixteenth years, and that thereafter the body gains slightly on the limbs. He also suggested that the chief defect in the growth of badly nourished chil- * Acad, of Science, St. Louis, March, 1893.
' Special Report of New York Juvenile Asylum.
64 THE PSYCHOLOGY OF ADOLESCENCE dren is found in the under growth of the lower Hmbs, but thought that colored children relatively excelled white in this respect.
Peckham ^ infers from the measurements of about io,cxx) children from four to eighteen that the growth of the body and of the lower extremities takes place in such a way that the length of the body of the girl is less than that of the body of the boy until the tenth year and thereafter greater until the sixteenth year. From fifteen to eighteen the bodies of girls grow only two inches and the bodies of boys over four inches. For the lower extremities at nine years of age, those of the girls are longer (as compared with the boys), at eleven shorter, and from twelve to fourteen again longer. At four- teen the lower extremities of the girls almost cease growing, while those of the boys increase by four inches between the ages of fourteen and nineteen.
The Chicago measurements ^ showed that in sitting height girls at fifteen began to increase more slowly and at eighteen appeared to have reached their maximum, while the Chicago boys grew steadily in body length till after eighteen, and then at a rather uniform but reduced rate until twenty and a half, when this census ended. The last Chicago percentiles show that while girls' sitting height is growing rapidly from ten to fourteen and almost ceases from sixteen to eighteen, it increases rather faster than net height from thirteen to fourteen and decidedly more slowly from eight to ten. In boys from sixteen to seventeen, sitting height augments more than net height and from nine to ten distinctly less. In other words, in- crease in pubertal trunk growth in both sexes both begins later and, relatively to limb growth, continues longer.^ Dafifner, who measured distances below and above the navel from ten to twenty-two, found that at birth the navel was 2.3 centimeters below the middle of the body; that be- tween the age of one and one year and a half it was at the middle length; then the lower part began to exceed the upper, so that at ten it was 21 centimeters; at eleven, 22 centimeters: * Sixth Report of the State Board of Health of Wisconsin.
' Report of the Department of Child Study and Pedagogic Investigation. Chicago, No. 2.
PARTS AND ORGANS DURING ADOLESCENCE 65 at twelve, 14 centimeters; at thirteen, 28 centimeters; at four- teen, 31 centimeters; and at twenty-two, nearly 34 centi- meters farther from the sole of the foot to the navel than from the navel to the crown of the head.
(b) Arms and Legs, Thorax and Pelvis. — The limbs prob- ably originate polymerously as outgrowths of primitive body segments, and precede in their development the pelvic and pectoral girdles that support them. From approximate identity in the fish the fore and hind limbs diverge in struc- ture and function, as we ascend the evolutionary scale. In the embryo the development of the bones of the Hmbs pre- cedes those of both the above girdles, but whether the pu- bertal increment follows this order is not yet determined. From data compiled from the latest works on anatomy, the following seem to be the chief adolescent changes in the bones of the limbs: The epiphyses of the humerus join the shaft at about twenty, the nucleus of the external condyle appears between thirteen and seventeen, that of the internal condyle joins the shaft at about eighteen and the other members at sixteen or seventeen. The superior epiphyses of the tibia join the shaft at seventeen or eighteen, and the inferior epiphyses at eight- een. The metacarpal bones and phalanges have epiphyses which join about twenty. The epiphyses of the clavicle ap- pear about the eighteenth year and join the shaft about the twenty-fifth year. The coracoid process of the scapula, which ossifies from two centers which join from the sixteenth to the eighteenth years, assists the clavicle in rotating the fore limbs outward farther from the trunk and in giving them greater freedom of motion. The gradual recession of the shoulders from the head; the gradual transformation of a fore foot into a hand and the greatly increased contact with the environ- ment thereby, the reduction of a prehensile to a human foot with growing mesial and degenerating external func- tions; the opposite bend of knees and elbows; the modifica- tion of the hip-bones for effective and varied motion, seem well-attested lines of evolution, but whether the pubescent bone changes are an advance along these lines or diversions from them, or neither, more genetic studies must yet de- termine.
6 66 THE PSYCHOLOGY OF ADOLESCENCE Landsberger^ found the span between the tips of the longest finger slightly less for most ages than body length. He also found that the forearm plus hand grew slightly less from six to thirteen than the upper arm. Quetelet ^ found it slightly longer, and Zeissing still longer. The " acromial breadth " of Landsberger or span minus length of arms increased regularly, but if this was measured from shoulder to shoulder in front, this anterior acromial breadth increased much faster.
In bone girths at the instep, elbow, and wrist, Sargent found boys from thirteen to sixteen to distinctly exceed girls; he also found that the length of the upper arm of girls from thirteen to sixteen is one-fifth of an inch less than that of boys, while the forearm and hand is three-fifths of an inch shorter.
W. S. Hall found that while the total height was increas- ing fastest the forearm was retarded, but, like the lower leg, at twenty-three resumed the same relations to total height that it had at nine. Moon says: '' In length from shoulder to elbow, the rate of growth appears to increase after the age of twelve, while in length from elbow to tip there is Uttle variation till the age of fourteen, when the growth is relatively quickened." In span of arms, Porter found a marked increase in boys at thirteen, which was greatest from fourteen to fif- teen, slightly less from fifteen to sixteen, and diminishing to eighteen. The year of greatest growth for girls he found to be from twelve to thirteen, the time during which the span of girls exceeds that of boys, in the main coinciding with, but lasting a little less than their superiority in height. Sargent found that among men the stretch of arms of only lo per cent was less than the total height, but that this was true of over 35 per cent of women.
In the legs the femur often has the greatest growth, both relatively and absolutely, and in giants and sometimes in acro- megalia is generally the bone most in excess of the normal. The epiphyses join the shaft in the inverse order of their appearance. The small trochanter joins at seventeen, the great at eighteen, the head at nineteen, and those of its lower extremity are * Untersuchungen liber die Korperliche Entwickelung der Fabrikarbeiter in Zentralrussland. Tubingen, 1889, p. 94.
* Das Wachsthum im Alter der Schulpflicht.
PARTS AND ORGANS DURING ADOLESCENCE 67 solidified at about twenty. In the tibia the lower epiphyses join the shaft at eighteen or nineteen, and the upper about three years later. In the fibula the same process takes place at the lower and later, at the upper end of the shaft, but two or three years after the corresponding processes in the tibia. The car- tilage of the patella is fully ossified only at puberty.
It has been often observed that the shin-bone or tibia is bent backward near its upper end and that its joint surface is inclined and enlarged; Henter ^ thinks this due to pres- sure in the fetal position. H. Charles ^ thinks that it is known to be caused by the habit of squatting or sitting on the heels, so common among primitive peoples; Retzius ^ finds it far more common in embryos than in adults, and thinks that these peculiarities are acquired characters inher- ited from an almost universal custom before chairs were used and found in the early stages of life in about all fetuses, but that it is gradually corrected among civilized races during growth.
W. S. Hall found that the increase in the height of the knee was relatively retarded during the three years when the mod- ulus or total height was rapidly increasing, but at twenty- three it had the same relation to it as at nine. Comparing the thigh with the crus, the latter reached its limit at the end of the sixteenth year, while the former continued to grow for at least three years. Moon found growth in height of knee retarded from eleven to sixteen, while length of body was rapidly increasing, and perhaps also while the thigh was growing fastest. If it is among the first lengths to feel the pubertal increment^ it resumes after a comparative pause, and is also among the last bone lengths to grow. Landsberger found that from six to twelve the length of leg increased from 60 to 80.6 centimeters. His figures agree very closely with those of Liharzik, although both are somewhat greater than the measurements of Zeissing and less than those of Quetelet. He, too, found leg growth greatest in the upper thigh.
Sargent found the difference in height between boys and * Anat. Studies. Virchow Archiv, 1863.
* Jour, of Anat. and Physiol., April, 1894.
* Biol. Studies. Neue Folge, vii, p. 61.
68 THE PSYCHOLOGY OF ADOLESCENCE girls from thirteen to sixteen to be largely due to the com- parative shortness of the thigh-bone in girls. " Although the body length is greater than that in boys, the difference, as shown by the sitting height, is largely due to the greater length of neck and head in girls, as shown by the superiority in boys in the height of the sternum."
Sargent says that the mean girth of the knee is about the same in both sexes, but the girth of the calf is two-thirds of an inch greater in girls.
Moon measured bone girths of boys from eleven to fifteen, and found that for knee, ankle, instep, elbow, and wrist, there was relative retrogression from eleven to thirteen, and afterward an advance till fifteen. In these dimensions the boy at fifteen has grown relatively larger than the man, except in the case of the instep, but this increase puts him still farther from the proportions he will have when mature. W. S. Hall, too, found that from fourteen to eighteen joint girths in- creased faster than bone lengths. Sargent found that from thirteen to sixteen boys have the start of girls in length of foot by half an inch, and in stretch of arms, by fully two inches.