From Fundamental to Accessory in the Development of the Nervous System and of Movements. // A DISSERTATION Submitted to the FacuIvTy of Ci^ark University in Fdi,fii- to the foot of the ^Journal of M. S., Jan., 1898. lO DEVELOPMENT OF THE NERVOUS SYSTEM. third frontal convolution (the Broca center for speech). Other smaller bundles are distributed to the first and second and third convolutions and also to the gyrus fornicatus. The most sig- nificant feature is that Broca 's .speech convolution iDegins devel- opment at a very much later period than other parts of the great areas concerned in general bodily movements. The order of development of the fibres in their approach to the cortex through the internal capsule is regulated by the same principle, we therefore .see, as those in the .spinal cord — tlio.se which perform the oldest and mo.st general functions mature earliest. The first of the .special sense centers in the cortex to mature, according to Flech.sig, is that of smell, which, according to Kndinger's .studies, is the first .sense center to be evolved in the biologic .scale, appearing as low as reptiles ; the last to mature is that of hearing. The process of meduUation of the fibres leading to and from the sense centers takes place rapidly, and by the end of the first month of human life, all of them show some evidences of maturity. Up to this point Flechsig's anatomical contributions rre accepted generally and much that he has put forth on the.se lines has been corroborated b}' other neurologists. But in the matter of the fibre connections of the cortex with lower ner- vous centers, he offers a revolutionizing contention in brain localization and his claim is now under the fire of criticism and dispute. Heretofore it has been the accepted theory that the entire cortical area sent or received fibres to and from the lower centers. Flechsig, from his examination of infants' brains, declares this is not true. Only about one-third of the cortical area at the end of the first month shows these descending jr ascending fibres. Then medullation begins to appear in the other areas, in the frontal portion, in the large posterior parietal area and in the Lsland of Reil, covering in all two-thirds of the human cortex. But contrary to expectation, basei upon the suppo.sition of previous methods of determination, these medul- lated fibres do not come nor go from the lower brain centers. They give no evidence of a peripheral .source or destination. They do not follo^\ the cour.'^e of the fibres developed in the first month of life. On the contrary, Flech.sig contends, the source and de.stination of medullated fibres of the.se larger cor- tical areas are in the .sen.se centers previously developed — tho.se of sight, hearing, touch, smell and taste. Since they are of different anatomical connection and direction, the conclusion is necessary that they must have a different function. Flechsig leaves his anatomv at this point to offer the plausible specula- tion that these large centers have for their function the as.so- ciation, and the superior directive power of inhibitive interfer- ence upon the areas of sense impressions. " Only one-third of DEVEI.OPAIENT OF THE NERVOUS SYSTEM. II the human cortex," he concludes with some pardonable elo- quence, ' ' stands in direct relation with the processes which bring sense impressions to consciousness and excite the inuscies and mechanism of movement ; two-thirds have directly with these nothing whatever to do. They have another, a higher function ' ' — the function of knowledge, of interpreting experi- ence, of the aesthetic sentiments, of the scientific decisions, of the moral judgments, etc. Through disea.se of these highest association areas, if w^e may follow Flechsig in some daring speculation, the individual is thrown back for the determina- tion of his conduct upon the sense or lower centers. vSuch, he suggests, is the effect of alcoholic intoxication, and other more permanent forms of mania. It is undisputed that in idiots and imbeciles, Flechsig' s areas of association are notably .small. Flech.sig goes further and claims upon anatomical evidence that in monkeys instead of two-thirds of the cortex being de- voted to the.se associations, there is but one-half; among car- nivora, these centers are very small and decrease as we descend the scale of mammals, disappearing entirely in rodents. It might be well, since Flechsig' s conclusions are now being tested by criticism, to draw a line between his anatomical con- tributions and his speculations. Unquestionably he has con- clusively shown that certain bundles of fibres, repre.senting certain more or less specific movements, mature at distinctly different periods. Regarding his as.sociation centers, it must be admitted that Flechsig has here contributed po.sitive data of anatomical observation that the sen.se centers are indirectly as.sociated in a common -Tea. As positive data, it cannot ije contradicted by theory or mere argument — we must wait for positive data of contradiction. Dr. Ross in his Diseases of the Net-vous System was perhaps the first to attempt a distinction in the nervous system between structures which in function antedate the human form of the organism and those which have been adde*"' during the period of human evolution. He says : " The poitions of the nervous system which man pos.sesses in common with lower animals and which are well developed in the human embryo of nine months, I shall call the fundamental part, and the portions which have been superadded in the cour.se of evolution, which diflferentiate the nervous system of man from that of the high- est of the lower animals, and which are either absent in the human embryo or exist only in an embryonic condition, I shall call the accessory part of the nervous system." Dr. Ross points out that the main movements which distinguish man from the lower animals are those which he has acquired since he adopted the erect posture — the varied movements of the hand in prehension and tool-using which developed after the 12 DEVELOPiMKNT OF THE NERVOUS SYSTEM. hand ceased to be merely a foot ; the movements of articula- tory organs concerned in speech, and movements of facial ex- pression. Dr. Ross, by this suggestive juxtaposition of funda- mental and accessory physical parts in the human organism, with the fundamental and accessory mental powers of man, has opened a field of inquiry rich in suggestion for psychology and education. Are these accessory movements of the hand and the articulatory organs, in some intimate connection with that mentality of man considered as accessory developments to those of the lower primates ? Have these accessory elements, by virtue of their comparative newness, more instability and plasticity, and are they therefore more subject to education ? Lastly, and most important in the development of the individ- ual, is the order the same as that of the race, so that from infancy to manhood we have a procession of developing parts beginning with the oldest and most fundamental and ending with the newer and accessory? Granting, for example, that the physical development follc^ws this order, does mentality as well ? If so, and if we can follow this order of development in some detail, we should have a principle that long has been needed for clearer visualized thinking in psychological and educational science. We must not neglect in this very brief consideration the very probable theory, happily named by Baldwin ^ the " short-cut" theory, by which development in individual man, by ages of modification, cuts across lots, thus escaping many needless bends and turns in the road evolution has actually travelled. Unless we accept this modification it would be impossible to explain many anomalies ; for example, the fact which Gratiolet has pointed out that, while in the embryonic development of the ape, the tempero sphenoidal convolutions (embracing the human auditory center) appears first and the frontal convolu- tions last, in man the order is reversed. Man does not complete his fundamental development at birth. If we are to accept Flechsig's association areas as the centers of human reason, we find these parts, anatomically, far down the vertebrate scale. From an objective study of human activity as illustrated by movements, the suggestion would be that these accessory structures are delicate modifications of existing structures. — new duties added to old forces. Ross thinks we have indirect evidence of these accessory formations in the huge development of the prefrontal lobes, which have pushed the posterior parts of the brain over the cerebellum, made the Rolandic fissure seem furthei back, relatively, and forced the posterior limb of the Sylvian fissure into a more horizontal position. 1 Mental Development in the Child and Race, p. 21. DEVELOPMENT OF THE NERVOUS SYSTEM. I3 Flechsig's contributions of data go far to enrich and sub- stantiate the theory of Ross by showing an evohition in the order claimed. But Flechsig's facts deal wholly with infancy and must be taken merely as the beginning processes of devel- opment. From the evidences of late growth of fibres shown b>- Kaes and Vulpius, and of cell bodies by Hamarberg, there is justice in assuming that these processes continue until late in life under regulation by the principle which requires the more gen- eral and fundamental structures to develop before the accessory. If this indeed be true, then it is clear that the historic peda- gogical contention, stated in the preface, that the order of instruction should be regulated by the order of internal devel- opment of the mind, rather than by the logical order of the subject-matter studied, rests upon a substantial basis. The Level Theory of the Nervous Syslenr. The conception of the nervous system as an undifferentiated unity, such as pervades the popular notion of mind, is not a view that finds substantiation by modern investigation. The notion that all our actions are dictated from a single center, the brain, is at best but half a truth ; many actions which have every appear- ance of good sense are regulated entirely within the spinal column ; and some from within the walls of the abdomen. The lower orders of animals have no brain ganglia, and the lowest vertebrates no cerebrum. Man epitomizes the products of biologic history, and from an evolutionary stciMdpoint we should expect a nervous system of added parts instead of a homogeneous organ. All positive evidences from the sciences of anatomy and physiology, and pathological phenomena as well, go to support the evolutionary view of the nervous sys- tem of parts, correlated and closely associated, but nevertheless preserving a degree of relative independence. It was some thirty years ago that Dr. Hughlings Jackson, the eminent English pathologist, made practical application of the evolutionary theory of the nervous system to the diag- nosis and treatment of epilepsies and mental diseases. Such has been the practical success of this application, that the so- called Hughlings-Jackson three-level theory is now the estab- lished basis of English diagnosis, and, in the words of a reviewer/ it has established system where previously all was chaos. Jackson conceived the nervous mechanism as composed of three systems arranged in the form of a hierarchy, one upon the other, the higher embracing the lower yet each preserving ^ Dr. James Anderson in Hack Tuke's Dictionary of Psychological Medicine. 14 devei.opmp:nt of thk nkrvous system. for itself some degree of exclusive independence. The lowest level is composed of those cell structures which receive im- pulses without physiological break, from the periphery or non- nervous tissues and those which discharge impulses into such tissues to produce movement. This has also been called the reflex level for it represents the type of simplest reflex and involuntary movement. Jackson localized these structures in the grey matter of the spinal chord, medulla and pons. His second, or middle level, comprises those structures which receive sensory impulses, not from the periphery nor from the non-nervous tissue directly, but from cells of the lowest level ; the motor cells of the middle level discharge, not into non- nervous tissue directly, but into the motor mechanisms of the lowest level. If we say that the lowest level " presents " im- pulses, then, in Jacksonian phraseology, the middle level "represents" them. Anatomically, Jackson included in the range of these middle level structures the cortex of the central convolutions, the basal ganglia and the centers of the special senses in the cortex. Evidence for such a level lies in the fact, now proven by the process of secondary degeneration of nerve fibres, that there are no fibres extending continuouslj' from the periphery or muscalature to the cortex nor in the reverse direction. In all cases they extend as continuous fibres only to the vicinity of cells of the reflex level in the cord, medulla and pons, as Jackson held. Jackson's highest level, as the topmost layer of the hierarchy, bears the same relation to the middle level centers as the middle to those of the lowest level. He presumes upon no continuous connection between highest and lowest level — the middle level structures mediates between them as a system of relays. The highest level, therefore, " r estab- lished than others of the same cla.sses respectively. Ready-made Complexes. We may begin by illustration of vome of these singular complex co-ordinations which Minerva- like appear full-fledged at birth. A striking example of this class is offered by Dr. Robinson* in experiments upon the ability of new-born infants to hold themselves suspended by grasping a finger or a bar. If we accept the current theory that the immediate ancestry of man lived in trees as many species of monkeys now do, this movement, though highly complex, involving the combination and co-ordination of several muscles of the arm, wrist, and fingers, is, in an evolutionary sense, fundamental. Dr. Robinson has kept records of experiments upon sixty infants, carried out within an hour after birth in the case of at least one-half of them. The infant subject was allowed to grasp a horizontal bar, or a finger, and left suspended in this way, sustaining its own weight. He says that in every case, with only two exceptions, the child was able to hold on " for at least lo seconds : in 12 cases with infants under one hour old half a minute passed before the grasp relaxed, and in three or four nearly a minute. When about four days old I found the strength had increased, and that nearly all when tried at this age could sustain their weight for half a minute. At about a fortnight or three weeks after birth, the faculty appeared to have atiained its maximum, for several at this period succeeded in hanging for over a minute and one-half, two for just two minutes, and one infant of three weeks of age for two minutes and thirty-five seconds." iMrs. W. S. Hall: First 500 days of Child's Life, Child Study >ronthly, Dec, 1896. ^Mrs. K. C. Moore: Mental Development of a Child, Psy. Rev. Monograph Supp., No. 3. ^ Darwinism in Nursery, Nineteenth Century, Nov., 1891. DEVELOPMENT OF THE NERVOUS SYSTEM. 35 Dr. Robinson remarks that the feat is one which would tax the powers of an adult. Wallace has recorded a similar condi- tion of the infant monkey's grasp ; one which had seemed secured a hold upon his beard clung so tightly that Wallace was not able, without help, to free himself. In similar vein Dr. Mumford^ has made an interesting speculation showing the analogy of certain very early movements of the infant to the paddling movements of water animals. He thinks them survival movements of aquatic life. These movements he points out disappear early in the first year, or are modified to form elements of more complex movements higher in the evo- lutionary scale. The feat of hanging from a stick or finger by the hands, logically would imply the prior development of the arm, shoulder, wrist and finger movements. But such are not the facts. The child grasps a stick and hangs suspended by his arms, long before he is able to pick up any object, or put his two hands together or lift hand to mouth. Logically, the grasp of the whole hand would follow the grasp by the parts, but observation shows us that a certain kind of complex grasp is one of the earliest movements, developed long before some of the very simplest finger movements. Any logical explanation fails at this point. Evolutionary explanation is plausible, for so far as the positive evidence of observation goes the more fundamental and older racial movements appear before the newer and less fundamental, regardless of the order of com- plexity, except in so far as the accessory as a rule tends to be more complex than the fundamental. If the human adult or child, beyond the age of infancy, grasps some object, as a saucer or a cup, so large that he cannot put the fingers around it, the arm will be extended toward the ' object, thumb uppermost, the palm facing upward. The thumb plays the chief role ; the last joint hooks over the rim and presses firmly downward, while the fingers underneath press in an opposite direction. This is not the Simian method. The Simian thumb is not strong nor motile enough for one reason, and in the second place it is not its habitual form of grasp. The thumb in the monkey is comparatively of little use, and, as already stated, some species are lacking in the muscle of its chief control. The fingers are used chiefly as a single hook, and in the most arboreal species^ the fingers have grown together to form a grasping hook. With them, the hand in grasping is used in just the reverse form. The fingers are uppermost, thumb underneath, the palm downward, and the grasp is accomplished by the fingers pressing downwards ^Survival Movements of Human Infancy, Brain, No. 79, 1897. iBuckman: Babies and Monkeys, Nineteenth Century, Nov., 1894. 36 DEVELOPMENT OF THE NERVOUS SYSTEM. against the palm. Infants follow the method of monkeys, not of man. Give a baby a saucer, or better a glass of water, and note that the rim is seized by the hand with the palm down- ward, instead of upward as in the case of an older person, while the thumb plays the role of a useless fifth wheel to a wagon. By what process is the transition to the adult form of grasp accomplished? Undoubtedly imitation is the final directing cause, but there is a functional difficulty in the retarded devel- opment of the infant's thumb. He is born with a monkey thumb and must first obtain a human thumb and be able to use it in perfect opposition. Preyer, Mumford and Mrs. Win- fred S. Hall have given detailed descriptions of the develop- ment of the thumb. For the first two or three months of life the thumb is really a nuisance to the child and is continually in the way. Generally it is curled inside of the grasp. In the case of Mrs. Hall's child it was not till the nth week that the thumb was brought outside the hand when the latter was clenched. On the fifth day. Axel Preyer clasped with his fingers his father's finger and it was not until the 12th week that there was certain evidence that the thumb was reflexly brought into use, and even in the 32d week, the movement was not entirely perfect. Mrs. Moore's child was first observed to use the thumb in opposition during 12th week, but she records that it was not till the end of the first year that this method had become estab- lished. In the case of Dr. Mumford's child in the 12th week, the diary records : ' ' Does not use his thumb properly for grasping ; when he tries to bring the bottle toward him he tucks the thumb out of the way. For the past fortnight he has begun to grasp with his fing-^rs." In the i6th week therer is this record : ' ' Has been using his thumb more and more and now never shuts it inside but always outside." In the 28th week, the last record given, we learn that "Grasping movements are much more perfect but still he does not pick up things between the tip of the thumb and finger. Occasionally he grasps a thing between the last joint of the thumb and finger." Mumford concludes that it is often six months before the development of thumb make the elaborate move- ments of the human grasp possible. While the thumb of the hand is thus gradually gaining in motility arid strength in a human directio7i, the great toe is losing motility and strength, also hi a hmiian direction, Robinson ^ attests from a number of experiments upon new born infants of an English work- house, that young infants curl their toes over anything grasp- ^ British Med. Jour., Dec. 5, 1891. DEVELOPMENT OF THE NERVOUS SYSTEM. 37 able. When either the palm of the hand or the sole of the foot is touched, the reflex grasp of the fingers or toes is occa- sioned. Buckman observes that a baby can move any of its toes independently and can move them one from another so as to make a V between any of them. Preyer records that on the seventh day, his child grasped a thin pencil by his toes exactly as by the hand.^ As the child grows older this power is lost. It is a movement which in the development of humanity has been lost. Mumford records that*in the 28th week the toes of his child had lost almost completely the tendency to grasp. Several other hand movements could be more or less defi- nitely traced, commencing in the infant with complex reflexes, inexplicable as yet upon any theory except that of evolutionary origin, and developing into human forms by modifications and additions that show no trace of logical arrangement. Among these to which reference might be given are the change from rhythmical sluggish movements of the fingers (which Mum- ford considers a survival from aquatic habits ) to human quickness ; development from the hooked form and use of the fingers,- to independent movement of finger ; the habit of using the index to poke about in investigating crannies or new objects ;^ the method of grasping a ball, etc. These constitute but one class of elements with which the child commences his career. They are not simple in the sense of logic for they are not complexes made up by co-ordination of several simple movements previously possessed ; the infants who hang sus- pended by the grasp do not usually grasp objects which merely touch their fingers ; the grasping reflex is only set off by touch in the palm of the hand."* Nor do all these complex but original co-ordinations appear immediately at birth. They are scattered along through infancy and childhood suggestively corresponding to the devel- opment by distinct parts observed in the growth of the nervous system. The teasing and bullying instincts of children offer suggestive illustration. Among the commonest movements in these activities may be observed ;^ pursuing, throwing mis- siles, striking, throwing down, holding down, dancing about conquered victim, laughing, clapping hands, pulling hair, pulling ears, etc. Children's natural games are largely made up of mild forms of these elements, the more malevolent ten- dencies having been elided. Whence came these movements which children acquire without effort and which they execute ^Senses and Will, p. 245. ■■^Buckman : Ibid. ^ Mumford : Ibid. ■• Mrs. Moore, S. and W. 243. ^Burk : Pedagogical Seminary, April, 1897. 38 DEVELOPMENT OF THE NERVOUS SYSTEM. with such natural grace and precision. They have no utilita- rian bearing upon the duties of civilized life. A plausible hypothesis classes them with the grasping reflexes of new- born infants — habits common to the race in its primitive condi- tions and carried forward in the structure of the lower le\'els of the nervous system. The.se complex movements are ultimate units; they do not conform to the purposes of civilized human conduct and are not explicable nor reducible by any process of logical explanation. Corresponding to them are psychic states of equal complexity which find no explanation in the civilized child's present en- vironment. There is a principle well known in ph3\siology and embryology, that a structure or a movement — useful for a certain purpose in a certain stage of the biological scale, loses this purpOvSe in a higher stage and through modification be- comes used for some entirely different purpose. This is what Wundt terms heterogony of purpose. Thus as we have .seen the fingers have been used for locomotion, then for seizing, grasping, and finally, in man, their ancient purpose is wholly lost, and an entirely new series of uses has taken its place, though the bony structure has not materially changed. Now what are the applications of this view to many of these strange com- plexes that appear in early childhood, even to include such seemingly evil forms as those which appear in cruelty, bully- ing and teasing? May it not be, indeed, that they constitute a level in the evolutionary hierarchy, and though in them- selves useless, are nevertheless an essential platform ft.:>m which the co-ordinations of a higher and useful level are formed? It is plausible that the child needs to live to some extent the life of his ancestors in order actually to develop in his own ner- vous system the kincesthetic sensations which by the process of higher evolution may serve as the basis for higher forms of activity in the highest levels? It becomes indeed a question of extreme nicety to determine just the exact moment when sufii- cient actual experience has fully established the racial tendency and the time for inhibition and radiation of the force into higher cerebral associations should follow. Danger of arrest of develop- ment at the lower stage is as important as that the fundamental impressions should not be made. Such a view gives these curious phenomena a natural place in child life, and empha.sizes the probability that children's plays and games, as mild vacci- nation forms, serve as mediations between brutal ancestral ten- dencies in the nervous system, and the higher levels employed in altruistic modern life, between savage racial action and civil- ized ideation. Co-ordination of Simple Movements. One who watches a young infant will notice a number of jerky movements contin- DEVELOPMENT OF THE NERVOUS SYSTEM. 39 iially occurring in practically all the muscles of the body. Some are merely slight twitchings of fingers and small muscles, and they range in scope to those of flinging hand, forearm, or whole arm about vigorously; the legs are moved in the same way. In the same class we must place the play of features, turnings of the eye and various other awkward movements. In some of these movements Mumford finds a rhythm which he thus de. scribes. "Slow rhythmical movements of flexion and exten- sion of the fingers occur, which instead of possessing the quick- incisive character of voluntary movements partake of the slug- gish rhythm so familiar to the visitors to the tanks of an aqua- rium. They often occur In a series of three at a time during a quarter of a minute ; then follows a pause during which there is apparently an accumulation of energy in the nerve cells. Then another series of spontaneous discharges takes place, to be in turn followed by another pause." Preyer has described the whole class of these movements as "impulsive" and labors to show that they are "spontaneous" impulses from the nc-vous system, occurring without external stimulus but exclusively by organic or nutritive processes. This clear-cut division which excludes all external stimulus probably is to be seriously ques- tioned, but this is immaterial for the present. Notwithstand- ing the evident fact that these movements possess strength and energy,^ the new born infant is unable to direct his hand or arm movements. He cannot for some days or even weeks bring his hand to his month. Accidentally, in these movements, the hand frequently is thrown to the mouth and the infant sucks his finger ; he is unable to remove the thumb from his mouth and must wait till some adult or lucky accident of movement removes it for him. Without purpose and without manifest external stimulus, the elbow, wrist, and finger joints are con- tinually being flexed. Even months before birth these pur- poseless movements had commenced. What is the significance ? As Flechsig has shown, in earliest infancy, practically the whole cerebral cortex is scarcely connected by mature fibres with the centers of action in the spinal cord, medulla and pons. It is not till well into the first month that these earliest connec- tions are made on the sensory side, and the motor connections by which activity is cerebrally directed donot appear until after the sensory has developed. The child is several months old before all portions of the sensory bundles of fibres which pass from the cord to the cortex show maturity in every part. These movements are most common in the earliest weeks of infancy, and tend gradually to disappear. The fact that the ^The strength, under specific stimuli, is demonstrated by the grasp and the power of bodily suspension. 40 DEVELOPMENT OF THE NERVOUS SYSTEM. connections of the lower centers with the cortex are not made till late, leaves us to conclude that these early movements are the products of spinal activity, uncontrolled as yet by the higher levels. They are lowest level movements in their sim- plicity, unmodified by the inhibitions of later human expe- rience which lie undeveloped in the higher strata of the ner- vous system. They must represent the movements which are racially the oldest entering as elements into human activity. If lower animal movements do appear in human activity, it is in this period we most safely can look for them in their most undifferentiated form. Later in infancy the first connections with the cortex are established. Then .sensory fibres go up- ward, and later motor fibres go downward from these middle centers, to inhibit and control the lower movements in certain particulars. Associations of cell with cell, center with center, develop to modify and make more precise or offer greater alter- ations in these modifications. Later, a still higher system of control is superpOvSed upon this. From this point of view, the purposeless movements of infants are more intelligible. They are movements without higher inhibition, movements as yet without halter or rem. The objective evidence bears out this supposition. Gradually, this flopping of arm, rhythmic flex- ions, and extensions, and nervous twitchings tend to disap- pear. Just in proportion to the capability of an infant to exe- cute voluntary movements of a given limb or organ, these vagrant movements disappear. The two opposed processes are gradual, and Warner^ records that at three years micro- kinesis, as he terms it, is still present. It is questionable that these movements ever do completely disappear, as experiments upon the ataxiagraph show. In form, these purposeless move- ments may be, as Mumford and others claim, survival move- ments of past ancestry. As such they are useless and sense- less, and if this were their only significance they well might be destroyed. Nevertheless they unquestionably have a far more significant place. Children without them are idiots.'^ The modern will theory certainly gives them a functional place. Before a movement can become voluntary, certain sensadons of the muscles, skin, joints, etc., occasioned by this movement, must be recorded in memory. These sensations, in form of memory deposit, become the stimuli by which voluntary action is directed and controlled. By these memory traces, just the exact amount of force, the direction, and the method of pre- cision is measured out, when a given movement comes to be voluntarily employed. Sully gives an apt description of this 1 Mental Science, April, 1889, p. 36. -Tuke's Dictionary of Psychological Medicine, p. 469. DEVELOPMENT OF THE NERVOUS .SYSTEM. 4I process in an infant eleven weeks old.^ ' ' Among the objects that attracted him was his mamma's dress, which had a dark ground with small white flower pattern. His hand accidental!)' came in contact with one of the folds of her dress lying over the breast. In a dozen times or more he repeated the movement of stretching out his hand, clutching the fold and giving it a good pull. A hasty rea.soner might easily .suppose that the child had now learned to reach out to an object when only seen. But the sequel showed this was not the case. Four weeks later, the diary observes, the child as 3'et made no attempt to grasp an object offered to him. The clutching was thus a blind movement. Yet it was doubtless a step in the process of learning to grasp. ' ' A simple explanation would be that the kinsesthetic impuLses consequent from the first acci- dental reaching and clutching served as stimuli by which the action was repeated, and so on till fatigue set in. In the light of this consideration, the importance of these rhythmic movements, be they survivals of aquatic and arboreal life or not, is manifest. If through any disorder, the lower levels are unable to produce them and the infant lies quiet and motionless, these sensations, necessary for willed action, never occur, the physical concomitants of mentality are never stored, and the infant lives to become an idiot. The.se movements, the flotsam and the jetsam of spinal activity uncontrolled as yet by higher centers, are the ultimate units. If we admit that they are survival movements we have here an illustration of a wide- spread physiological principle, that new uses are grafted upon old structures. The modifications of the ultimates, whether complex or com- paratively simple, with which the infant begins life, proceeds in several directions : ( i ) the breaking up of old bilateral and simultaneous tendencies, characteristic of central movements ; (2) the growth of independent movements of .smaller parts that previously only moved in conjunction with larger wholes ; (3) the co-ordination of various series to form long and complex sequences as we finally find them illustrated by writing, .sew- ing, piano-pla}'ing, etc.; (4) the development of precision and accuracy ; and finally (5) the response of different movements to a great variety of different stimuli. The.se modifications perhaps represent the chief accessory lines of development that distinguish human movements as such. Any attempt to give a concrete review of these movements would of course require a volume. Merely a few typical illustrations will be made. Under head of bilateral tendencies which give way to inde- pendent movements, Mrs. HalP reports that during the first 1 Studies of Childhood, p. 413. ^ Ibid. 42 DEVEI.OPMENT OF THE NERVOUS SYSTEM. few months the right hand was always carried to the mouth with the simultaneous movement of the left hand. ' ' Even when putting the thumb to his mouth he used the left hand in this way, and finally held the left hand under the right hand while sucking the right thumb. If the left hand was confined so that he could not use it in this way, it was noticeably harder for him to put the right hand to his mouth, while it always annoyed him, causing him to cry." We must be careful not to confuse the age of a movement with the age of a child. I think it is probably true that any new hand movement attempted at any age tends to be bilaterally simultaneous. For example, chil- dren of an}'' age, in learning to play the piano are able only after considerable practice, to make movements independently with each hand. Few adults, without practice, will be able to move the left hand in a circle to the left while the right is making a similar circle to the right. Hancock experimented upon 142 children asking them to pat the top of the head with one hand while they made a circular motion about the breast with the other. Forty-five failed entirely, while the others were more or less successful after a time. Bilateral movement is older than independent movement of the hands ; the former doubtless is the order of the lower levels ; it is overcome by control from the higher accessory centers. The formation of a successive series from parts previously existing may be illustrated by the following type described by Mrs. Hall. The age of the child was 13 months. "After watching two children play ball he was allowed to join the game. The ball was rolled to him, he picked it up, then lean- ing far forward placed it upon the floor, but could not push it away. His hand was repeatedly given an impulse which sent the ball forward but even then he could not roll it alone. The ball was thrown to him and he tried to return it, but after raising his arm and reaching the hand forward he could not propel the ball. Again he was assisted in making the requisite motion and when the ball left his hand he screamed with delight. After playing fifteen or twenty minutes, he raised the arm as if to throw the ball, then opened his hand and let it drop out but was unable to give it the forward impulse. The game was played daily and each time at the beginning of the play he experienced the old difficulty ; but each da}' he succeeded after fewer trials than were necessary on the previous occasion, and finally learned to throw the ball in an awkward way. By the 58th week he had become able to throw it in the general direction of his effort, and by the 60th week to throw it with ease and with con.siderable accuracy. ' ' In this description the difficulties of nervous co-ordination are clearly outlined. The child had already mastered all the DEVELOPMENT OF THE NERVOUS SYSTEM. 43 movements taken separately, but while these nerve centers could act separately, their co-ordination, not only in a general order of discharge, but in order of delicate nicety of time, was impossible. The forearm must be extended at just the exact moment and the ball released at another precise moment. When we consider the infinite complexity of the whole process our wonder is that it is so quickly acquired. The suggestion leads to the query whether or not movements of similar com- plexity, but entirely new in racial experience, are learned as readily in later life. I hardly believe they are. Throwing is almost an exclusively human movement though some monkeys have been known to possess it. In strictly human experience, however, it is old and firml)' established. May it not be pos- sible that the explanation for the comparative ease with which the child learns this movement be accounted for on the theory that in learning he is retracing paths in his nervous system, more or less distinctly established b}* ancestral experience ? An adult required to perform a movement of similar complex- ity but entirely new in human experience would not learn as readily and rapidly as the child of thirteen months. Some such supposition is necessary to account for such facts of which this illustration is but a type. A more complex type of co-ordination, though it represents a much earlier period of life, is illustrated by the following comical instance.^ " In the 17th week the breast was shown to him while he still held his thumb in his mouth, and then for the first time he seemed to realize that the two were sepa- rate and he must release the thumb before obtaining the breast. Up to this time the thumb had been removed for him, but on this occasion no assistance was given him until he himself had made an effort and had failed. He looked at the breast, then worked at the thumb, then cried, but could not take it from his mouth. He was therefore assisted and given the breast. Each time he nursed he was required to make the effort to re- move the thumb, and was afterwards given such help as was necessary. Late the next day, after a long trial and some cry- ing, he succeeded in his efforts, whereupon he made a little sound of satisfaction and seized the breast. Six days later he was able to remove the thumb at will and with ease." Leav- ing out the writer's interpolaton of mental motives, which, perhaps, are not essential, we might, perhaps, express the physical conditions something as follows : In the form of accident, so to speak, the ner\^ous apparatus is matured suifi- ciently to place the hand to the mouth and also to remove it ; further, there is established already a co-ordination between 1 Mrs. Hall : Ibid. 44 DEVELOPMENT OF THE NERVOUS SYSTEM. the centers of smell or of sight, so that when stimulated suit- ably, they excite the movements necessary to take the breast ; but the presence*of the ungovernable thumb prevents. We clearly have here the separate parts of a somewhat complex co-ordination, but co-ordination is wanting. We know cer- tainly that at this age, four months, .some paths to and from the central convolutions of the cortex are matured, especially on the sensory side. Of all sensations that would fir.st develop, on account of their early use, we must conclude that those con- cerned directly and indirectly with sucking would be conveyed there. Of all kinaesthetic sensations of arm and hand move- ments which also would be likely to be the earlie.st to develop in the middle cortical level, those of movement of the hand to and from the mouth would be first, for these are the earliest acquired movements. For six days this hand is specifically trained in removing itself, in close association with sensation from olfactory, visual and hunger centers that are clamorously importuning that something be done, and that something be done quickly. An accident in the path of predisposition solves the difficulty for the first time. Each repetition of it makes the transit easier. The co-ordination is established and it is established in just the same way that racial infancy has established it. Gradually higher centers are developed receiv- ing impulses from the lower, co-ordinating them anew and discharging inhibitive motor impulses, substituting or adding other movements. These, at a still later period, are made the basis for a similar superposition. The earliest progress of a child in movements is in the realm of what is racially fixed and determined. Only with the maturing of the highest cen- ters, factors of extreme plasticity, choice, freedom from racial predisposition are introduced. This brings us to a point of view of the highest pedagogical significance, to wit, that in the development of co-ordination from lowest to highest, the power of evolutionary habit decreases, and the possibilit}'- for special modification increases; that there is a progress in teachableness, or at least the term, education, must be taken in two different senses. In the lower strata of development, where the steps have been worn by racial experience, education that is most serviceable will be that which takes its cue from the racial stimuli and concerns itself with leading co-ordination to take these fixed steps as truly as possible. But later, as the higher strata are reached, when the movement emerges from this deep worn gorge that ancestr}^ has trodden and comes to the point where racial paths are divergent and indistinct, the definition of education changes. Education has now a wider sweep of vision, and instead of following paths, may sight distant goals and lead DEVELOPMENT OF THE NERVOUS SYSTEM. 45 more directly to it. In a different terminology we might call this early education which is restricted to aiding the child to follow in the steps of his ancestors " fundamental," and that which finds its place later, that which comes in when racial paths grow shallow and divergent, and originality more possi-. ble, we might call "accessory" education. Taking wider range in this thought, we may consider the child as the sum of his movements. We must remember, nevertheless, the prin- ciple of development by parts, by which some parts reach maturity at later periods than others so that we can never say, in an exact .sen.se, that the child is now in the '• fundamental " period of education and then in the "accessory." But in a crude, inexact way, it is certainly true that more lines of accessory education are possible in adolescence than in child- hood, more in childhood than in infancy. Using the word " teachable " in the accessory sense, we may say that the child is far more teachable than the infant. Dr. Harris has said that education must be governed chiefly by the needs of objec- tive environment. This assertion is too universal. It is education defined only in the accessory sense. A teacher with only this view plays the part of the bull in a china shop in deal- ing with those mechanisms of fundamental education which would require us merely to follow racial traces. There is a familiar dispute in pedagogy whether or not the child should be always allowed to follow his inclinations. One party maintains the extreme position that we should follow blindly the child's interest. Another party stands aghast at the proposal. From this present standpoint taken must we not first discover whether a specific tendency in question is "fundamental" or "accessory?" If deeply fundamental, we must follow nature. If the tendency is one in its accessory period of development, we may perhaps allow objective factors largely to determine. The child traverses before he is six or seven years old, not only the long deep worn road of racial ancestry, reaching back perhaps as far as arboreal or even aquatic life, but I think we may say, betakes a few paces in certain few co-ordinations that are his own, blazes a few trees and leaves his mark. As we shall later see, by six years of age, he shows evidences in many lines of being far upon the highway of distinctively human capabilities of movement. His fingers and hand that once tended to act only upon the lower simultaneous principle, now can move in fair degree by the principles of independence, and of succession. In the delicate steadiness of central movements and the complex co-ordinations requiring delicate peripheral movements, he has probably acquired half of the ability he ever will acquire. His nervous system has made a prodigous 46 DEVELOPMENT OF THE NERVOUS SYSTEM. growth — far outstripping any other system. The co-ordina- tions which have made this possible are the products of this growth. Development of Hand Movements During School Ages. The present chapter will undertake to review briefly the few studies which have been made upon children of school ages by psycho-physical methods, to determine the rapidity, accuracy, strength and maturity, and fluctuating periods in the develop- ment of hand movements. The data, incidentally, however, is suggestive for many other pedagogical problems. Rapidity of Movement. Dr. W. L. Bryan, Mn Worcester, and Dr. Gilbert at Yale^ and Iowa," have experimented upon the degree of rapidity with which children of different ages were able to tap an electric key which automatically recorded results. Dr. Bryan thus tested four sets of arm muscles — shoulder, elbow, wrist and metacarpo-phalangeal finger-joints. In order to secure the free separation of these .sets of muscles, the arm of the subject was clamped by means of certain devices to allow movement only of the specific set of muscles. The test in all cases was the greatest pcssible number of taps the subject could execute in five seconds.'* The number of children (public schools of Worcester) used in the results here referred to is 729. They ranged in age from 5 to 16 years. The following tables for boys and girls give the arithmetical mean of the tests (right arm) of all boys, and of all girls of a given age. Tabi,e a. — Boys. Age No. Finger . Wrist . Elbow . Shoulder 5 6 7 8 9 10 II 12 13 14 15 14 26 35 33 43 37 36 33 34 41 32 19.6 195 21.0 23.1 24.4 55-2 27.0 293 28,7 31-5 31.6 20. 1 23.0 23-7 26.3 27,8 28.3 30.3 31-6 32.3 33 -o 34-2 22,7 23-5 24.2 26.1 28.2 28.1 29-3 29.9 31,0 32.7 31-5 18,4 19.8 20.5 22,3 24,1 22.6 24.1 25,0 25-5 27,2 26,3 16 26 33-9 35-9 32.7 28.7 Girls. Age No. Finger . Wrist Elbow Shoulder 6 7 8 9 10 II 12 13 14 15 28 32 33 43 37 36 33 34 41 32 19.8 20,7 22.2 24.0 25.8 27.1 28.2 30.3 295 29.1 21.6 23.1 24-3 25-5 28.5 304 31-^6 33-2 30.3 30.9 22,7 23.2 24.4 25-4 27-5 28,6 29.4 30-5 28.8 293 19,9 20,2 21,9 22,7 22,6 24.9 25-7 27-5 26.6 26.0 16 26 31-3 33-3 30.1 27,9 1 Development of Voluntary Motor Ability, Am. Jour. Psy.,'i>io\. 1892, '^Studies from Yale Psy. I^ab,, Vol. I. ^ Univ. of Iowa Studies in Psy,, Vol. I. •*The mechanism and conditions are so complex in detail that the reader must be referred to the original article for them. DEVELOPMENT OK THE NERVOUS SYSTEM. 47 Dr. Gilbert has made two studies upon rapidity of tapping, one upon New Haven children and one upon Iowa children. In his tests the elbow was held free from the table and the arm was in no way clamped. The subject tapped with the finger but the movement must be interpreted largely as that of a wrist movement. The number of children was approximately 50 for each sex and each age, from 6 to 17 years of age. The num- ber of taps in five seconds for both sexes is shown by the fol- lowing table : Tablk b. Age New Haven Boys Iowa Boys . . New Haven Girls Iowa Girls . . 21. o 22.1 19.7 22.8 23-3 8 24.9 25.8 21.2123.9 22.3I24.2I26.0 lo 25.827.7 27.1 28.3 25.0 26.9 26.726.2 II 29.7 28.1 27.8 28.0 12 30.3 30.1 29.6 29-3 13 ! 14 29.8 3I-I 28.1 295 31.2 32.4 28.0 29.4 15 31-3 34-0 29.8 31-3 16 330 34-0 31.8 32.2 17 350 34.4 31-5 33.8 18 36.0 34.3 19 36-7 35-3 Without holding Drs. Bryan and Gilbert responsible for the form of all conclusions, we may draw from their studies the following inferences : I. The rapidity of motor ability of the hand and arm, as in- dicated by tapping, increases, on the whole, with age and does not reach maturity until the adolescent period. The results of both Dr. Bryan's and Dr. Gilbert's studies agree in demonstrating this fact conclusively. The rate, though subject to several fluctuations, very significantly in- creases from six years through the pubescent period. The immaturity of this movement at the age of entering school is shown by the following table of percentages, assuming the rate of tapping at 16 years as 100 per cent. Tabi,e C. Per cent, of i6-yr. ability possessed at 6 years of age. Per ceut. of t6-yr. ability acquired between 6 and 16 years. Boys. Girls. Boys. Girls. ( Bryan. ^ Finger . . Wrist . . Elbow . . Shoulder . (Gilbert Hand (N. H. Hand (Iowa) ) 57 64 69 64 65 65 75 71 62 69 43 36 28 31 36 35 37 35 25 29 38 31 None of Dr. Bryan's tests are directly comparable with Dr. Gilbert's, since the subjects in latter held the arm entirely free, 48 DEVELOPMENT OF THE NERVOUS SYSTEM. and their movement, therefore, is probably a combination of all four of the movements studied by Dr. Bryan. This fact of the comparative immaturity of children's motor ability excites the pedagogical inquiry whether or not in the existing school requirements, stick laying, needle work, pencil work, etc., of the kindergarten (children under 6 years), and in the writing and drawing of primary children there is in- telligent realization that the child's ability, so far as rapidity of movement is a symbol of maturity, is only 60 to 70 per cent, of what it is at 16 years. II. Girls mature earlier than boys In rapidity of hand and arm movements. This is manifest by a glance at the tables. As shown in Table C, the girls in all but one test (New Haven) have, at 6 years, reached a larger percentage of their 16-year ability than the boys. At 13 years girls have reached practi- cal maturity, and the rate in some of the tests actually de- creases after that age. Bryan's girls at 13 years have acquired 97 per cent in the finger test, 99 per cent, in the wrist test, roi per cent, in the elbow test, and 98.2 per cent, in the shoulder test. In general, therefore, we may say, girls reach practical maturity in rapidity of nrm and hand movements at 13 years, while boys increase ver> materially their ability after 15 years of age. III. The rate of improvement in rapidity is not regular from year to year, but proceeds by very marked fluctuations, or rhythmical vibrations. Sometimes the rate is very rapid, and again slow, even in some years showing a decrease from the rate of the previous year. Both Bryan's and Gilbert's tables agree in showing four periods of acceleration and four periods of retardation in rate between the years 6 and 17, though there is slight divergence for specific years. The years of highest rate for boys are as follows : Worcester, 8th and 9th, nth, 14th, i6th. New^ Haven, 8th, lothandiith, 14th, i6th. Iowa, 8th, 12th, 14th and 15th, i8th. The years of lowest rate are as follows : Worcester, loth, 13th, 15th. New Haven, 9th, 13th, 15th. Iowa, nth, 13th, i6th. Rapidity of movements of hand and arm, in tapping, tends to be greatest when the rate of growth in height and weight is least, and vice versa. This relationship is shown by comparison of the annual rate of growth in height, weight, as given by Dr. Gilbert, and, in the case of Worcester children, by measurements and weigh- ings taken by Dr. G. M. West. In making the conclusion we need not necessarily presume upon any organic relation DKVELOPMKNT OF TIIK NKKVOUS SYSTKM. 49 between rapidity and the growth rate, but it is probable tliat the processes of rapid anabolisni in the addition of new tissues, at least interferes with the dexterity of movement. In Bryan's data the loth and 15th years, wliich are the lowest in tapping ability, are the highest in growth rate. In the New Haven study the years of retarded tapping ability are the (jlh. 13th 15th and 17th; while the years of accelerated growth rale are the 9tli, nth, 13th and I5lh. V. The more central (fundamental) movements tend to mature earlier than the less central (less fundamental) move- ments. Dr. Bryan's tests, which deal with the movements of shoulder, and elbow, wrist and finger, separately, offer evidence upon this point, though perhaps strictly speaking, no one of these move- ments, except ♦hat of the finger, can be considered exclusively accessory or fundamental. In table D this relative immaturity of the finger movement is clearly shown. At 6 years, the finger has acquired, in both girls and boys, a di.stinctly smaller per- centage of its ability at 16 years of age, than any of the others, and the wrist movement is less developed than elbow and shoulder. It has been shown that growth in power proceeds by rhythms and it becomes interesting to know in quantitative form the relative amounts of development that are added within each of these rhythms of advancing age. Table D is constructed with a view of showing this. Each retardation with its suc- ceeding acceleration is considered a period ; there are thus in the case of bo)^s four periods : 6 to 9, 9 to 12, 12 to 14, 14 to 16 ; in the case of girls three periods: 6 to 10, 10 to 13, 13 to 16. The tapping ability at 16 years is taken as 100 per cent., and the figures in the columns indicate the percentage of this 16-year ability added in each of these respective rhythms: TabivE D. Boys^ Right Arm. Age .... Up to 6 years. 6-9 ; 9-12 1 12-14 14-16 Total at 16. Finger . . . Wrist .... Elbow . . . Shoulder . . 58 64 72 69 14 14 14 , 5 15 7 7 4 9 4 7 8 5 100 100 100 TOO Girls' Right Arm Age .... Up to 6 years. 6-10 10-13 13-16 Total at 16. Finger . . . Wrist .... Elbow . . . Shoulder , . 63 65 75 71 20 21 15 ID 14 14 10 18 3 I 100 100 100 100 50 DEVELOPMENT OF THE NERVOUwS SYSTEM. These tables show : ( i) that in both boys and girls alike, the elbow and shoulder movements have reached a larger percent, of their mature power than the finger and wrist movements ; of the two classes the finger is doubtless more of an accessory movement and of later evolutionary development ; (2) that the finger movement acquires a large per cent, of its ability after nine or ten ^/ears of age — 28 % in the boys and 17.5 % in the girls. Dr. Bryan, by a different series of calculations, reaches the same conclusions and says : "These results show that the shoulder grows most slowly and the elbow slightly faster, the wrist and finger very much more rapidly." A table stating the number of taps, the elbow, wrist and finger exceeds that of the shoulder, at each age, shows that while this surplus in the case of the elbow is only slight through- out the period from 6 to 16 ; in the case of the wrist, this surplus doubles and increases from six to sixteen fold. The wrist and finger do not gain materially upon the shoulder until the I ith year and then the finger rates, relatively, spring for- ward at a greatly accelerated rate. The explanation suggests itself that the shoulder as a central movement has passed the period of extreme nascency very early, the elbow follows, the wrist makes its gains still later and the period of nascency for the finger is certainly not till after 10 years of age and probably does not reach its real culmination in power until sixteen years. Such nascencies have important significance in the management of manual school work. Development of Streyigih. Peron early in this century showed by experiments with the dynamometer that Malays and the natives of New Holland are distinctly inferior, in strength of the hand and arm, to French marines. That the civilized races are distinctly superior in hand and arm strength to the lower races of man has man}^ times since been confirmed by Manouvrier^ and others. M. Fere goes further and contends that among indi- viduals of the same race, the more intelligent have the greater strength of hand. He says^ that the same dynamometer test, taken upon individuals belonging to different classes of society, have shown that the pressure produced by the effort of flexing the fingers is less with workmen whose profession is exclusively manual than with those whose work requires less muscular force, but whose intelligence comes more into play ; and fur- ther, that the muscular power is still greater with those of the liberal profession of the same age. The close intimacy of men- tality and hand force is demonstrated by M. Fere's well known 1 Rev. Philos., 1884, Vol. I, p. 645. -Rev. Philos., Vol. XLI, p. 623. DEVELOPMENT OF THE NERVOUS SYSTEM. 51 dynamometric experiments^ showing that the power is very significantly afiFected by emotional and intellectual states. A subject whose dynamometric force is normally 50-55, shows a decrease to 45 when affected b}' a disagreeable odor, while an agreeable one causes an increase to 65. In another subject the odor of musk raises the force from a normal 23 to 46. Music and colors produce similar varying effects and various intel- lectual states show no less pronounced influences. Fer6 for- mulates the law from his dynamometric tests that the energy of momentary effort is in proportion to the habitual intellectual functions. The few statistical studies which have been attempted upon the development of strength during the growing years of child- hood and adolescence have been made by Dr. Porter upon St. Louis children,^ Dr. Gilbert upon Iowa* children, and Mr. Rob- erts in England. * The following table gives the absolute annual increments of strength obtained by subtracting the test of one year from that of the next. Dr. Porter's test was made by means of the dynamometer, an instrument which registered mainly the hand-grin power, which, as we have seen, involves one of the mo.st fundamental movements appearing in the first hours of life. Dr. Gilbert's wrist lift involves the hand and fingers, but the principal strain is upon the wrist. The arm Tabi,e E. Porter. Gilbert. Roberts. Gilbert. Haud-squeeze. Wrist-lift. Arm-lift. Arm-lift. Auuual Annual Annual Annual AGE. increase in kg. increase in kg. increase in lbs. increase in kg. B. G. B. G. B G. B. G. 6}i to 1% . . 1.6 1.4 1-7 1.0 8.4 6.8 1% ^Yz . . 1-7 1.6 0.8 1.0 9-5 4.1 s>i 9;^ • . 2.0 I.I I.I 0.0 1.0 7.2 6.5 9/2 io>^ . . 1-5 1.2 1-7 1-5 O.I 9.6 -1-3 10/2 iiYz . . 1-5 1.4 0.5 0.5 2.3 9-5 7-7 11^2 T-^Yz . . 2.3 1-7 1-7 0.1 1.0 1.2 7-7 6.3 12>2 nY2 . . 2.4 2.7 I.O 1-9 5-7 3-5 8.6 II-3 13/2 T^\Y2 . . 3-2 1-9 I.I 0.6 2.8 3-2 12.8 6.4 14/2 I5>^ . . 44 2.0 4.6 1.2 6.0 4.1 23.0 5-4 15/2 i6>^ . . 4.4 1.8 3-3 .6 9.6 2.2 8.3 -3-2 16 'i 17K . . 0.1 3-3 •4 6.4 2.1 20.0 2.8 17/2 i8>^ . . 0.0 1.2 2.2 5-0 13.6 1.4 IH>2 19>^ . . 1-7 0.0 1-5 1-9 0.0 3-8 ^Sensation et Mouvement. -Growth of St. Louis Childreu, Trans. Acad. Sch., St. Louis, March, 1893- '^Ibid. ■• Report of Parliamentary Commission on Secondary Education, Vol. V, p. 363. 52 devp:lopmknt of the nervous system. lifts of Roberts and Dr. Gilbert test fingers, wrist, elbow, and shoulder. They are therefore not safel\- comparable one with the other. I have arranged them, however, in parallel columns to show whatever parallelism there may be in additions of strength taken in a general sense. It is clear from this table that strength varies from year to year in rhythms as we have observed in all other tests. The chief accelerations begin in boys from 13 to 14, and continue probably almost until 18 years. In girls the period of accelera- tion begins a year or so earlier, and, as a rule, begins to de- cline from 15 to 16 ; there seems to be a new acceleration after 18 years. From 6 to 10 or 11 years occur periods of gradual increase with very marked fluctuations. In order to determine the relative proportions of increase that occur in different periods I have calculated the following tables. The strength at 16 years has been taken as a base or 100 per cent. By sub- traction the other columns are obtained. Tabi,e F. Per cent of Per cent of Per cent, of i6-yr. strength Per cent of i6-yr. strength i6-yr. strength acquired be- i6-yr. strength acquired be- acquired by acquired by tween 6 and tween II and 6 yrs. II yrs. II yrs. 16 yrs. Boys. Squeeze (Porter) 20 46 27 54 Wrist (Gilbert) 21 46 26 54 Arm (Gilbert) 24 64 22 44 Arm (Roberts) 36 Girls. Squeeze (Porter) 23 54 31 46 Wrist (Gilbert) 32 65 32 36 Arm (Gilbert) 32 67 23 45 From these calculations it would appear that in the case of boys only about a fifth of their 1 6-year-old strength is acquired before 6 years, a quarter from 6 to 11, and over one-half from II to 16, during the pubertal changes ; in the case of the test upon the whole arm maturity is somewhat in advance. In the case of girls a greater share is acquired before 6 years, their strength acquirement is more rapid than with boys from 6 to 1 1 years, although the largest increment is added also during the pubertal flux. These tests shed little light upon the question of the order of fundamental and accessory, since each of the tests largely involves fundamental movements exclusively. But in so far as the lift of the entire arm may perhaps be more exclusively fundamental than the combined movements of the wrist and hand alone, we see from the table that the arm movement seem to mature earlier than the wrist and hand. DEVELOPMENT OF THE NERVOUS SYSTEM. 53 Mr. L. W. Kline, in a statistical study of truant children,^ finds that these children are significantly less developed, phys- ically, on the average, than children of the public schools. He has kindly given me the data of dynamometer tests which he made, but did not use in his publication. These tests were made upon boys from 9 to 14, inclusive, in the Massachusetts truant schools. He also made identical tests upon a number of cliildren attending the public schools of Worcester. While the number of children tested is not as large as desirable, nevertheless, a distinct cleavage is shown between the two classes, and goes to support the other evidences which indicate that hand strength, as well as motility, is in direct relation with the degree of mental development, or what is probably the same thing, strength depends to some extent upon the nerve centres of the higher levels. The following table com- pares the strengths of the truants and normal children : Tabi,e G. Truants. NORMAI,. ge- No. Mean Strength. No. Mean Strength 9 19 23 69 26 ID 20 25 83 30 I I 30 30 102 38 12 31 36 121 40 13 47 40 102 46 14 23 51 • 90 53 Dr. Gilbert, in Iowa, segregated the " bright," " average " and "slow" children, according to their teacher's judgment. While in some tests, e. jr., rapidity of tapping, there 'was shown a distinct line of cleavage in favor of the bright chil- dren, yet in the tests of wrist and arm lift no cleavage is shown. Unfortunately, however. Dr. Gilbert combined the figures for both boys and girls in this comparison. There is a fact of probable significance that the rate of in- crease in strength is high throughout the pubertal periud, especially during the year in which the pubertal sexual changes chiefly occur, 14 to 15 in girls, and probably 15 to 16 in boys. In other tests there is generally a retardation during this particular period, the chief acceleration in height and weight occur before and after. The peculiarity is of signifi- cance in connection with a theory that has many supporters, that the seminal fluid has a direct effect upon strength. The relation is one which has been recognized from the time of the Greeks, who practically observed it in the training of their sol- ^ Pedagogical Seminary, Jan., 1898. 54 developmp:nt of the nervous system. diers and athletes. Bierent^ has developed this law, and the facts these tables express are in agreement with his conclu- sions. The literature of strength — increases after seventeen years, with which we shall not deal — is very voluminous. The inves- tigations which have been made indicate conclusively that growth in this direction is by no means at maturity at the age mentioned. The English Anthropometric Committee con- cludes that the increase is rapid, and then more slowly until 30 years, after whicli it tends to decline with an increasing rate.^ He finds a parallelism between the increases of weight and strength. Precisio7i of Hand Movements. Superficial investigation shows that the nervous mechanism involved in the attempts to be pre- cise with the finger, require first an adjustment of a larger area of muscular and nervous tissues than those of any other movement of the body probably. Precision in drawing a fine line accurately, for example, requires steadiness not only of the finger movement itself, but of the hand, the whole arm, and even of the body. If we observe a child learning to write we find that he holds his breath, and in many cases his legs will be found bracing his body in intense strain. The central muscles of the arm and trunk are called into activity to give support of steadiness as a necessary condition for the fine ad- justment to follow.^ We may, therefore, perhaps consider pre- cision as involving two processes : ( i ) that of steadiness of the central organization as a platform upon which rests (2) the finer nervous adjustments of the most complex nerv^ous ele- ments. I.. Ce7?lral Sicadhicss. This phase of the problem has been subjected to investigation by Hancock^ in the effort of children to stand still. The subject was asked to stand with feet close together and hands at side, to keep his attention on a distant object, and to try to remain still for a minute. By means of the ataxiagraph attached to a cap worn on the head the bodily swayings of the subject are automatically registered upon smoked paper. ^ The test was made upon 168 boys and girls of Worcester, 5 to 7 years of age. His tests show that during these two years the girls gained in steadiness 32 or 33 percent. 1 La Puberty. 2 Report of Anthropometric Committee, p. 37. •''Compare Mercier : Nervous System and Mind, pp. 94-97. Also V€rh, Rev. Philos., Dec, 1897. •* Preliminary Study of Motor Ability, Fed. Sevt., Oct., 1894. ''The swaying in adults has been similarly tested by Bullard and Brackett, Boston Medical and Surgical Journal, Vol. I, p. 136, and Vol. II, p. 136; also Huisdale, Am. Medical Journal, Vol. XCIII, pp. 478-485 DEVELOPMENT OF THE NERVOUS SYSTEM. 55 of the power of control at five years ; and the boys gained about 15 or 16 per cent. We may say, therefore, as the indication of Professor Hancock's study, that power of central control in- creases with age (very rapidly at the ages 5 to 7), and more rapidly in girls than in boys. Mr. H. S. Curtis in a .study of inhibition tested the ability of children of various ages in their ability to sit ab.so- lutely still. He concludes: "The ordinary child cannot sit still voluntarily. Children under five years do not on the average sit still more than 30 seconds and children from 5 to 10 years not more than one minute and one-half . Mr. Curtis explains this condition on practically the same ground offered in the paper, viz., that the higher centers of voluntary control are not developed in any degree of maturity until a late period of child life. He finds that mental occupation materially assists in the control of nuiscular restlessness and that these higher centers of brain action are not developed until a com- paratively late period. Johnson experimented upon feeble-minded children,^ 7 boys and 5 girls, averaging 13 years, by the same method that Han- cock used. He found the average swaying slightly greater at this age than Hancock found among the normal children of five years. The former were of a high grade intelligence for their class. (2) Peripheral Unsteadiness. Corresponding to these larger swayings of the central movements, there are numerous small vibrations in the peripheral mu.scles involved in the adjustment for fine movements. Though these movements are impercep- tible to ordinary observation, they are always experimentally demonstrable. In early infancy the.se movements are more noticeable in the form of apparently nervous twitchings that constantly occur in nearly every muscle of the body, even during sleep. As has been stated, these are perfectly normal and are signs of health ; they tend to disappear in conditions of lowered nutrition, and in idiot infants they are very much fewer or wholly absent.^ As the infant grows older, the}'' gradually grow fewer and less noticeable. The fact that they gradually tend to disappear may be explained on the ground that as the nervous and muscular mechanism is perfected, the lower mechanisms pass under control of higher brain levels. Dr. K. H. Lindley'* has made a study of the automatisms of early childhood and he shows the persistence of manj'' of these earlier simpler forms into childhood and even into ado- lescence. Though in later childhood many of these simpler ^ Ped. Sent., Vol. Ill, p. 282. ''Hack Tuke's Dictionary of Psychological Medicine, p. 569. ^ Am. four. 0/ Psychology, July, 1896. 56 DEVELOPMENT OF THE NERVOUS SYSTEM. movements are combined to form rather complex automatisms, as Dr. Lindley illustrates, nevertheless a large number remain below the threshold of ordinary obsen^ation, indicating a more or less incomplete co-ordination of motor discharge or storing of sensory impulses. Such co-ordinations clearly must inter- fere, as they are greater or less, with perfection of precision in fine finger movements requiring absolute steadiness. Dr. Lindley found that automatisms increase very perceptibly with fatigue, that they are most frequent in accessory muscles and, in general, decrease with age. Professor Hancock ^ made an experimental test to determine quantitatively the unsteadiness of the .shoulder, arm and hand, by means of the tremograph. He tested by this means 25 adult men, 62 bo3\s and 34 girls from 5 toy years. The ability of the boys of 5 years was from one-tenth to one-fifth of that of the adults, and the ability of control improved about 50 per cent, from 5 to 7 years in the case of the boys and less for the girls. The girls posses.sed a much more mature control than boys of the same age. (3) St'?isorv Fa dors z?i Precision. What has been said of these swaying tendencies of central and peripheral movements offers us evidence of the interfering factors which enter the problem of precision. A second .series of conditioning factors in obtaining precision, lies in the sensory development. A movement is determined, the modern view of voluntary move- ment holds, by the .sensory kinsesthetic impressions which are .stored up in memor}-. A movement is made, at first acciden- tally we may say, and the sen.sory impressions from skin, joints, etc., which in consequence are stored in memory, are used in future discharges of motor impulses. Precision will depend upon their number and the accuracy of habitual ad- justment between them and motor discharges. Clearly, as experimented facts show, exercise (J. e., the frequency with which they are impressed upon the memory) will go far to determine motor precision. The effects of exerci.se upon sensibility of skin is brought out clearly by Fere."^ A subject more or less regularly practiced flexing his fingers singly, moving them in laterally and bringing them separately into opposition with the thumb. Sensibility before and after the experiment was tested by Block's instrument for finding the lea.st pressure of a millimeter square that gives sensation. This test applied to the fleshy pnrt of the thumb and finger tops showed that, on the right hand the thumb had gained 32 per cent, in sensation ; the 1 Ibid. ■^Rev. Philos., Dec, 1897. DEVELOPMENT OF THE NERVOUS SYSTEM. 57 index, 15 per cent. ; the middle finger, 10 per cent. ; the ring finger, 13 per cent. ; and the little finger. 6 per cent. ; on the left hand, the thumb gained 37 per cent. ; the index, 11 ; the middle, 7 ; ring, 5 ; and little finger, 8 per cent. The development in accurac}' of these kincesthetic sensa- tions with increasing age, has been neatl}' demonstrated by Dr. Gilbert in his Iowa study. ^ The subject was seated before a table upon which were two points 50.8 inches apart ; a pencil in his hand was placed at one end of the line. After carefully noting the distance, his eyes were blindfolded, and he was asked to move the pencil along the board and place it as near as possible upon the other point. Five trials were allowed each subject. Averages of these estimates from 50 subjects of each sex and for each age from 6 to 19, are as follows (the fig- ures give in centimeters the averages for each age of the estimate of the distance, really 50.8 cm.) : Age, 6 7 8 9 10 II 12 13 14 15 16 17 18 19 Boyr-. 10.7 31.2 38.144.446.546.744.746.7 46.5 50-3 51-5 53-i 54-9 57-1 Girls, 12.7 20.3 29.7 31.8 38.9 46.5 41. 1 43.2 48.3 46.7 51. 1 51.0 52.1 51.5 The progre.s.sive development with age is clearly shown. (4) Growth in Precision. Dr. Br3'an,^ with a somewhat elaborate mechanism, tested precision of finger movement as it occurs in executing the motions of writing. He used in the test some 600 or 700 boys and girls ranging in age from 6 to 16. He states in conclusion that, "the most obvious fact whicli appears is the great gain which is made between 6 and 8. Almost one-half the gain in precision made from 6 to 16, in both ' up ' and ' down ' writing movements, is acquired between 6 and 8 years. A second test to which Dr. Bryan subjected the same children was that of their ability, with a stylus, to strike a fixed point. An electrical apparatus re- corded the approximations of error. The boys' right hand from 6 to 16 years gains in ability 60% ; the boys' left hand, 55% ; the girls' right hand, 56^0; the girls' left hand, 58%. The pubertal period seriously interferes with the growth in maturity and the chief gain is before pubert}'. Professor Hancock" tested some 160 children, 5 to 7 years, in threading a needle, sitting still, holding arm horizontally, attempting to suppress twitching movements, tapping with the fingers in various orders, tying strings, etc. Mr. Hancock draws from them the following conclusions : ( i ) Children early learn to make movements involving large movements. They succeed easily in large movements of some degree of ^ Ibid. '' Ibid. •^ Ibid. 58 DEVEI.OPMKNT OF THE NERVOUS SYSTEM. complexity. The order of development of control is, evidently, body, shoulder, arm, forearm and hand. In hand control the index finger differentiates before that of the others. (2) Fine and complicated movements are made with difficulty. (3) Children in normal healthy growth show a lack of co-ordina- tion and control paralleled only by ataxic, choreic, and para- lytic patients. A test having a similar significance was used by Dr. Gilbert in his study of New Haven children. The subjects were given 10 weights, varying from 82 grammes to 100 grammes by steps of 2 grammes each, but indistinguishable in size. They were given the smallest weight as a standard, and asked to sort out the others which seemed to be of the same weight. The number of pupils tested was 50 for each year of age and sex, from 6 to 17. Dr. Gilbert thus summarizes: "The re- sults show a gradual increase in ability to discriminate from the ages 6 to 13. After 13 there is a gradual falling off of 6.8 granmies (in discriminative precision), and then another gain till 17. Boys and girls, considered together, gradually increase in ability, but when they are considered separately, marked dif- ferences of sex appeared." In the study, previously quoted, bearing upon characteris- tics of children who made "rapid," "normal" or "slow" progress in school grades under a system of promotion giving freedom to individuality, it is shown that 54 per cent, of the rapid pupils, 39 per cent, of the normal pupils, and 22 per cent, of the slow pupils are strikingly careful and accurate in their writing and drawing exercises ; while on the other hand, 11 per cent, of the most rapid, 34 per cent, of the normal, and 59 per cent, of the slow pupils are strikingly careless and inaccurate. From the evidence of this study we must link ac- curacy on the whole with a maturer mental development as indicated by school progress. We may sum up the matter of accuracy : (i) that as a pri- mary condition which makes accuracy of hand and arm possible, the child must have a matured degree of control under direction of his higher level centers (/. c, voluntary). The fact that this maturity is not reached, normally, until the ninth or tenth j-ear, renders questionable the efforts of the .school to compel accuracy such as is required by the kinder- garten, and also by the primary school, in writing, weaving, etc. (2) That the ability to be accurate in hand and finger movements increases very materially during school ages ; (3) that accuracy depends indirectl3^ upon the development of the body as a whole, the steadiness of the trunk muscles being as essential as the accuracy of hand or finger movements them- selves ; (4) that for purposes of delicate peripheral movements, DEVKLOPMENT OF THE NERVOUS SYSTEM. 59 as shown by ataxograpliic experiments, etc. , the child has not a matured power of control until well into the school period, and long after severe school requirements of accuracy are de- manded 1(5) that the evidence goes to show that the sensory kinaesthetic sensations, essential in psychological theory, for definite voluntary movements are, in general, in a very imma- ture state until eight to ten years; (6) that while the early years of school life are doubtless the period of nascency for fin- ger and hand movements, nevertheless there is evident need of a clear realization of these physiological conditions on the part of tedchers, not only intelligently to direct the training of these movements, but also to guard against unhygienic require- ments ; (7) that there are manifest dependent relations between general mental ability and power of accuracy of hand move- ments ; (8) that steadiness of the trunk or central movements (fundamental) necessarily precedes ability to be accurate in peripheral (or accessory) movements. In conclusion, some of the more general suggestions of this review may be restated briefly as follows : i . The brain grows in its finer structures until a late period in life. There has been a failure to substantiate connection of differences in mentality with the differences in gross anatomy of the brain- shape of skull, weight of brain, form of convolutions, etc. 2. The order of development of the independent parts of the physical and nervous system is, as a general principle (subject doubtless to minor exceptions) from that which is oldest in racial history towards that which is most recent ; that those portions which are oldest are most fixed, determined, and least capable of modification by present environment, and those which are relatively most recent are most plastic and subject to modification by education and environment. Among the important pedagogical inferences which follow from this prin- ciple, the following might be mentioned : 1. That, taking the activities independently, there is an early period in the development of each part or process, when the purpose of education must be to follow the fixed innate hereditary line of tendency, and to allow the racial instincts fullest play of development (fundamental education). 2. That there follows a later period, in an activity's devel- opment, when it passes partialh' out of the fixed control of racial habit, and becomes more plastic to present environment (accessory education). 3. That the order of logical connection of subject matter belongs, educationally, to the period of approximate maturity of an activity's development, and must not be introduced in 6o DKVEIvOPMENT OF THE NP^RVOUS SYSTEM. the earlier instinctive period, iu conflict with strong evolu- tionary tendencies. 4. In an extremely loose sense, clearly recognizing the principle that the organism develops by parts, each of which has a different time of beginning its development, a different rate of ripening, and a dififerent period of reaching matu- rity, nevertheless we may regard the period of infancy as one of predominating nascencies of the oldest fundamental activities largely in control of the lowest level of the nervous system ; the period of childhood from two years to puberty as the period of predominating nascencies of the special sense and their association one with the other : the period of adolescence as the period of predominating nascencies of the highest form of associations, i. e. , those which have been developed in the his- tory of the human race. 5. The child's hand at the age of commencing school is relatively immature in power of rapidity of movement, strength and precision. Roughly it would seem that at the age of six the child has acquired only about 20 to 75 per cent, of the power at 1 6 years of age. It is clear that the period from 6 to 10 years is one of extreme nascency. 6. Deficiencies in the structure of the hand and in freedom of its movements are significantly frequent as accompaniments of deficiency in intelligence. The human hand in early child- hood needs opportunity for the fullest possible development which in general proceeds from fundamental to accessory move- ments. This statement is consequently far from justifying many of the systems now employed in the schools which ignore the principle.^ 1 The educational writings of Dr. E. N. Hartwell, particularly his report as Director of Physical Training in Boston schools for 1894, are of especial value on this problem. References to his articles will be found in Mr. Louis N. Wilson's Bibliography of Child Study, 1898.