Some conclude that there is a diminished, and some that there is an increased variation between minimal and maximal rates for a time. How much of the retardation is due to increased size of the heart, which sometimes grows in a salta- tory way a fourth in a single year, how much to the tem- porary weakening of its power thus caused, how much to changed relations between general vascular capacity, or ten- sion, and the total amount of blood, or to other causes, is un- known. It is, however, due more to increase in height than to age, for the pulse averages slower in tall than in short people. Volkmann and Ramenaux have given mathematical formulae to express this retardation, and it has been found that the increase in frequency of heart-beats that follows the scale of decreasing stature, when carefully averaged for many cases, approximated the results obtained by calculation. De- ductions of height, however, from the number of pulsations, even though they could be made with a far greater degree of accuracy than has yet been attained, for averages will be found, besides having a certain theoretical interest, to be of some value as a basis from which to measure the wide range of individual variations. Curiously, the ratio of diminished pulse to increasing height is nearly the same whether computed for the differ- ent stages of growth or for adults of different height.
The strength of the heart-beat measured by the force of its blow against the thoracic wall was found by Poatain* * Clinique Medicale de la Charite. Paris, 1889.
92 THE PSYCHOLOGY OF ADOLESCENCE to be greater at puberty. Whether the growth of this wall renders it more elastic or the heart-beat grows really stronger as it is reduced in frequency, whether there is a new relation slowly established between elasticity of its walls and the vigor or mode of its contraction, is unknown. The frequent pal- pitations and unaccountable variations in rate and mode of action and other functional disturbances, which often awaken a cardiac consciousness so disquieting, without any danger- ous structural derangement, are among the more common experiences of this age, and are due, in part at least, to the change in size of the heart as compared with the lumen of the cardiac and other large arteries.
Although Gilbert's tests were only carried to the age of sixteen, his '' data point very distinctly to the accelera- tion of the pulse during the age of puberty for both sexes, both in the curves of normal pulse and pulse subsequent to fatigue. This effect at puberty seems more marked for boys than for girls."
The blood-vessels can not be isolated for weighing, so that their circumference becomes the most important meas- urement. It is inferred that the growth of the larger vessels and that of the smaller capillaries in general coincide, although only the former have been measured. Vierordt's table is as follows: Age.
Height.
Arteria pulmonalis.
Aorta ascendens.
Aorta tho- racica.
Iliaca com.
dextra.
Carotis com. dextra.
Subclavia dextra.
Years.
I4i-i6 cm.
20 mm.
22 27 29 The following is the best available table of diameters: Agb.
Arteria pu\- monalis.
Aorta ascendens.
Aorta renalis.
Carotis communis dextra.
Sub- clavia dextra.
Renalis dextra.
Femoralis dextra.
Years.
II. 2 50 PARTS AND ORGANS DURING ADOLESCENCE 93 The arteries continue to grow in size till at least the age of sixty. The best of all measurements of them begins at the age of twenty.^ The thickness of the arterial walls increases with age, but this probably occurs after the period of maximal increase of size, and involves diminished elasticity and ere- thism of most organs and tissues.
Of profound and far-reaching significance is the fact that before puberty the blood-vessels are large and the heart small. The latter now undergoes a great and often sudden relative increase. Landois says that from infancy to puberty the heart is small and the vessels relatively large, but in the adult, conversely, the heart is large and the arteries relatively narrow; so that there is a conversion of the relation existing between the size of the heart and the cross-section of the arterial system, taken as a whole. At birth the relation of heart to arteries is as 25 to 20; at the dawn of puberty it is as 140 to 50; and in full maturity it is as 290 to 61. The pulmonary artery is relatively large in infancy as compared with the aorta, but at puberty the two approximate the same diameter. Benecke ^ also thinks that before puberty the arterial system is larger relatively to the heart than after- ward, and sums up his view by saying: '' The larger the heart relatively to the vessels, the higher the blood-pressure, and the earlier this becomes the case, the earlier, stronger, and more complete is the development of puberty." A recent text-book sums up the matter by saying that the relation between the size of the heart and the width of the arteries is in children the reverse of what obtains in adults. " The ratio of the volume of the heart to the width of the ascending aorta before puberty is approximately as 56 to 20, while after puberty it is as 97 to 20." This means that there is almost double the volume to the heart's capacity, and as the arterial lumen is for a time unchanged, there is great increase of blood-pressure. This view is that the ratio of the weight of the blood to that of the body is increased after puberty.^ ' Schiele-Wiegand. Virchow's Archiv, vol. Ixxxii.
* Die anat. Grundlagen der Constitutionsanomalien der Menschen. Marburg, • Exercise during Adolescence, by Walter Truslow. Am. Jour, of Physiology, 94 THE PSYCHOLOGY OF ADOLESCENCE Arterial tension is also modified and blood-pressure is considerably augmented during adolescence, except in the lungs, where it is somewhat lowered in adults. Along with this goes, too, the slight increase of temperature at puberty, amounting on the average, according to the best estimates, to about i° F. Vierordt's figures give for the ages between three and fourteen an increase of from 138 to 171 millimeters quicksilver; in adults it is 200, while the measurements that indicate the lowest results give a rise from three to thirteen years of from 97 to 113 millimeters. This suggests, especially w^hen we consider the frequent anemia and chlorosis of this age, so common in girls, that while there is a distinct rise of pressure there is now, as in so many other respects, a widened range of variation not only between individuals and sexes, but in the same person at different times.
By the constant tension or tonicity of the walls of the ar- teries, which is maintained by the vaso-constrictor nerves, a high pressure of blood is always maintained in the arteries. As these divide toward the capillaries, the total cross-section of which is some six hundred times that of the aorta, pressure decreases and the rate of movement becomes very slight in the small and often negative in the large veins. Blood-pressure changes not only with every pulse-beat and respiration, but follows the longer and so far unexplained curves of Traube and Hering, and also the seasonal changes lately demon- strated by Zadek. With this increment of pressure at adoles- cence, together with a considerable increase of arterial cali- ber and the rise of temperature, is associated not only the increased metabolism and increased growth rate, but the necessity of mental and physical activity, the psychic inten- sity, need of excitement, and emotional prodigality so char- acteristic of the erethism of pubescent muscles, brain, stom- ach, and other organs, and the range of vascularity also widens. The importance of this action gives some counte- nance to the adage that a man's health and age are as that of the walls of his blood-vessels.
In the new-born child one-nineteenth of the body's weight is blood. This proportion decreases to one-thirteenth or one- fourteenth at maturity. It is never so variable in all its ele- ments as at this age. About 29.2 per cent of all the blood is PARTS AND ORGANS DURING ADOLESCENCE 95 found in the muscles at rest, but this amount is, of course, greatly increased by their action; 29.3 per cent is found in the liver; 22.76 per cent in the heart, lungs, and great blood- vessels; 8.24 per cent in the bones; 6.3 per cent in the intes- tines; 2.1 per cent in the skin; 1.63 per cent in the kidneys; 1.24 per cent in the brain and spinal cord. In the very young child a very large part of the total quantity of blood cir- culates in the skin. In hemorrhage or anemia it may be, at any age, reduced or increased. In general,' as Madden says in sub- stance, a new balafice is struck in the allotment of blood to the different parts ot the body at this period, involving in some parts congestion and in others discharge, the last relieving the former. This is connected with an increase in the relative amount of blood and the increased power of producing it, with menstruation and all of the other profound changes of ado- lescence.
Tables show that with adolescent growth between the age of fourteen and maturity there is a retardation in the time of circulation of the blood, an increase of from 97.4 to 180 grams thrown out by one systole, and at the same time an increase of from 141 to 218 grams in the amount per second that passes the aorta. The work of the left chamber of the heart is still more increased from 0.3134 to 0.5668 kilometers, while the blood that circulates per minute through a kilogram of the body is reduced from 246 grams to 206 grams.
Of the many determinations of red and white blood-cor- puscles, Schwinge's is the best. It is as follows for men: Red.
White.
I-io yrs cubic mm.
Thus while the red or white corpuscles seem to hold their own or perhaps sHghtly increase with slight variation, ^ Quain. Med. Die.
9^ THE PSYCHOLOGY OF ADOLESCENCE the white corpuscles or leucocytes decrease in the thirties and forties, but increase again later.
The number of red blood-corpuscles per cubic millimeter is high at birth (5,368,000). It seems to decline at five or six years and perhaps to reach its maximum in the later teens and twenties; but all these determinations are still uncertain. The extinction coefficient of hemoglobin, which is very high dur- ing the first week of life, seems to rise with the development of puberty, as perhaps does the relative number of white to red corpuscles. The number of white corpuscles is enor- mously increased in leucocythemia and in the process of inflammatory reaction to certain inflective diseases, and by digestion, and, as like the red corpuscles they are constantly breaking down, their numbers may be very greatly reduced and their vigor impaired by age.
The ancient idea that blood is the best index of an eu- genic race seems to have a certain confirmation in the studies that have been made on its specific gravity since Lloyd Jones's first important memoir^ in 1887. According to Sorensen, beginning with about 1,050 in both sexes in the third year, this rises on the average in boys till the seven- teenth year to 1,058, with little change thereafter till old age, w^hen it falls. In girls it rises till the fourteenth year to 1,055, 3.t seventeen drops a little, and remains some three points below that of man till about forty-five. The plasma alone, however, in woman has a sHghtly higher specific grav- ity than in man, with a distinct rise at puberty not seen in males. A sexual difference thus becomes evident at the dawn of adolescence. Menstruation both at its first onset and at each periodic return causes a slight reduction of the specific gravity of the blood. The period between fifteen and twenty-two, when variations in the specific gravity of the blood in girls are great and when it may fall very low, is called by Dr. Jones the age of anemia, and suggests that the chlorosis so characteristic of that period is an exaggera- tion of a state normal in old age. That specific gravity rises in women after the age of child-bearing is only another indi- cation that this sexual difference is associated with the repro- * On the Variations in the Specific Gravity of the Blood in Health. Journal of Physiology, 1887.
PARTS AND ORGANS DURING ADOLESCENCE 07 ductive functions. Variability in the quantity of serum, fibrin, alkali, carbonic acid, and hemoglobin, is known to be great, but so far these fluctuations have not been definitely associated with puberty.
D. Growth of the Lungs. — Lungs and chest share to a marked degree in the augmented development of adolescence. This is true whether inferred from girths of the chest expand- ed or contracted (which do not consider the movements of the diaphragm, which have not been measured), or by deter- mining the weight of the lungs from the cadaver at difYerent ages, or by recording the maximum amount of air that can be expelled into a spirometer. In the following table I have brought together averages from various tables, many of which are now at hand: Age.
of both boys. — mann.
.5 of both , boys.— rdt.
CA pacity, Chicago, 9* V bOC bO V bo a c Oh-l ^ > 0 > > 0 0 S P3 9 lO II 12 13 14 15 i6 17 I,COI,2 i8 4. II 19 20 21 22 46 23 24 25 26 Averaging records of Amherst students for twelve years, Hitchcock found that during their four years' course the in- crease was 7.1 per cent of their lung capacity on entering. It is certain that the lungs continue to grow in weight until old age. In youth they constitute from ij to 2 per cent of the body weight, while in mature years from 2^ to 3f per cent. Thus they outgrow the body, especially the alveolar cells 8 98 THE PSYCHOLOGY OF ADOLESCENCE which are vigorous and growing in extreme age, when the elastic fibrous tissue has begun to degenerate. According to Smedley, girls increase most rapidly in vital capacity from twelve to fourteen, after which the increment is at a dimin- ished rate and appears to end before twenty. Boys take a sharp start upward at fourteen, increasing most rapidly for two years thereafter, but continue a rather rapid rise till at least nineteen and a half. Smedley says that the difference between the greatest amount of air that can be expired after a forced inspiration into a wet spirometer has very marked increment during adolescence; is much greater in those trained to physical exercise; decreases with the amount of activity; and if taken in connection with size is an index of the rate of metabolism.^ In boys the rate of annual increase in this respect reaches its first maximum at fourteen; shows a very slight decline at fifteen; and reaches its highest maxi- mum at sixteen. Among all twelve-year-old children tested it was found to be much greater the higher their standing in the grades, and to be distinctly inferior in boys in a school for laggards.
In Chicago the greatest percentile differences in the vital capacity of boys is at sixteen, when it ranges from 2,400 to 4,200 cubic centimeters, and in girls at fifteen. In both, this is naturally just after the year of greatest aggregate measure.
Yearly increase.
94 93 Relation — Of the circumference of the thorax to vital capacity.
Of body length.
* Report of the Department of Child Study and Pedagogic Investigation.
PARTS AND ORGANS DURING ADOLESCENCE 99 Increase of thoracic capacity, on which the strength of the body architecture is so dependent, seems from the measure- ments of Kotelmann, Roberts, PagHani, Pesskoff, Erismann, Schnepf, and Wintrich to be of great significance, and to fol- low the curve of weight increment more closely than that of height. Correlating the figures of four of these writers, we have the results in the table on opposite page.
The normal enlargement of the heart at puberty is so great as to materially lessen the vital capacity. Careful measurements show, however, that this reduction is more than compensated by the enlargement of the thoracic space, due to growth, and more yet by increase in the surface of the pulmonary tissue, which in a man is about 200 square meters. Between twenty and thirty the right lung of the male, which ^s smallest at birth, becomes, according to Boyd, about one- third heavier than in the female. One of the now somewhat extended list of diseases, which are less liable to appear during pubescent acceleration of growth, is consumption, although whether adolescent development can regenerate pulmonary tissue already lost, as Lancaster ^ thinks, is a question which must for the present be left in abeyance.
The following is the interesting table of vital capacity from Pagliani: ^ Years.
M.
F.
Circumference of thorax. Boys (cm.).
8 Q 10 II 12 13 14 IC 16 17 18 iq Kotelmann ^ found the circumference of the thorax at the nipple to increase most rapidly in the fifteenth year; next ^ Lancaster. Psychology and Pedagogy of Adolescence. Ped. Sem., vol. v.
' Luigi. Sopra Alcuni Fattori dello Sviluppo Umano. Turin, 1876, p. 54. • Die Kdrperverhaltnisse der Gelehrtenschule. Berlin, 1879.
THE PSYCHOLOGY OF ADOLESCENCE most rapidly in the year before and the two years after; and then to decline up and down the age scale to nine and twenty- one, and this both absolutely and relatively. This in adults is about half the height, but for boys chest girth is more than half the height and increasingly so to fourteen, and then approximates the adult norm. As compared with body weight, on the other hand, chest girth increases more and more slowly. He found that vital or lung capacity meas- ured on the spirometer increases most rapidly during the sixteenth year, and declines absolutely and relatively up and down the age scale. However chest girth be taken — in inspi- ration, expiration, or rest — vital capacity increases more rap- idly than it. This increases more rapidly than height, but slower than weight. The relation between chest girths in maximal inspiration and expiration decreases with age, show- ing progressively less elasticity.
Beyer's ^ table of chest circumference is as follows: Age.
15 16 17 18 19 20 21 22 23 Moon's data for the ages below sixteen years are continued by the Amherst figures based on 742 students, where the same men in the classes from 1885 to 1901 were measured for three and one-half years: Moon Capacity Years. of lun^.
* Beyer, H. G. The Value to Physiology of Anthropometric Tests and Meas- urements in the Form of Statistics and their Importance to Education. Reprinted from the Journal of the Boston Society of Medical Sciences, May, igoi^ vol. v, pp.
PARTS AND ORGANS DURING ADOLESCENCE Amherst Numbers.
Chest Repose.
Lung Capacity.
Age.
Actual in mm.
Per cent.
Actual in liters.
Per cent.
30 73 49 27 12 13 7 44 40 22 Sargent found that while there was Httle difference in the natural chest of the sexes from thirteen to sixteen, boys show superior expansive power. In lung capacity he found girls from thirteen to sixteen to be seventy cubic inches behind boys, and far weaker in strength of expiratory muscles. Porter found that in the power of mean expansion of the chest, boys gained over girls almost steadily from eight, but with a sHght gain in the rate of their superiority from twelve to seventeen. In chest girths he found the year of most rapid growth in boys to be from fourteen to fifteen, and that it continued to be rapid to eighteen. In girls, he found the years of great- est increase in chest girth to be from twelve to fourteen.
In vital capacity the Chicago boys increased steadily but little from six to twelve. The next two years showed a marked increase, and from fourteen to sixteen came the great- est rate of increase, followed by diminution during the next two years. In vital capacity, the increment of Chicago girls was manifest before eleven, greatest for the next three years, with progressive decline from fourteen, and especially from fifteen to seventeen.
Moon found that chest power, which increased but little from eleven to thirteen, underwent very marked increase be- tween fourteen to sixteen, when his tests ended, as did lung power, although the latter was less marked. Strength of expiratory muscles and legs he found to develop earlier than those of back and forearm.
Landsberger's measurements show increase during the ages 102 THE PSYCHOLOGY OF ADOLESCENCE from six to thirteen from 52.3 to 60.5 centimeters in the cir- cumference of the body at the navel, but at a rate less and less each year than the height. Sargent found that girls from thir- teen to sixteen were i^ inch smaller at the waist than boys.
Zak ^ finds the circumference of the chest increasing fastest in the fourteenth and fifteenth years, viz., 4.1 and 3.6 centimet- ers respectively. An increased rate of chest girth began at thir- teen and one-half, and from sixteen and one-half it was less rapid but marked to eighteen and one-half, when it became slow but continued to increase to twenty-two and one-half, when his census ended. At all ages after twelve it was greater abso- lutely than that of rural and peasant children, whose most rapid increment was later and continued a year longer, viz., to nine- teen and one-half. Of thirteen of the best measurements made in various lands the Russian choir boys of Vasilyew excel all others from ten to fourteen, and the English boys of Roberts from fourteen to eighteen. Up to nineteen chest circumfer- ence is less than half the height and thereafter greater. From eleven to fourteen, both inclusive, it is nearly four centimeters less than half the height, this difference being greatest at thir- teen. In factory boys and in all other classes this inferiority of chest girth to half height either did not exist or was less marked at all ages to seventeen. No measurements have shown such marked inferiority of chest development in school-going youth.
Ling wished young men to increase one hundred and fifty- four cubic centimeters semiannually for a few years, and there are cases where running has increased chest capacity over three hundred cubic centimeters in three months. Some think exer- cise also gives increased efficiency of a respiratory surface of a constant size. Deep breathing, however caused, no doubt acts against auto-intoxication, gives increased power to resist dis- ease, is the root of endurance under effort, and is of great and hitherto unsuspected importance in determining the level or intensity of life, one of the chief variables with which the rate and completeness of normal oxidation of the blood is cor- related. The ratio of lung capacity to weight is very properly called the vital index. Training largely consists in taking off weight and adding lung power. In the interests of effective PARTS AND ORGANS DURING ADOLESCENCE respiration there is much to be said against the mihtary position required at the command " attention," because it so restricts the action of the diaphragm.
Frequency of respiration, like so many other functions, is very dependent upon size. The rhinoceros breathes six, and the rat two hundred and ten times per minute. The human infant begins hfe with from thirty-five to forty- four, and at fif- teen has settled to eighteen or twenty respirations per minute when at rest. For a score of years thereafter the rate normally varies but little.
Vierordt compiles the following interesting table show- ing the relation of vital capacity ch* the respiration content to height as follows: Age.
cm.' for I cm.
Height.
Hastings, on the basis of 5,496 children, gives the follow- ing interesting bases for comparison: Lengths (cent.).
Breadths (cent.).
Depth (cent.) chest.
Girths (cent.) chest ex- pansion.
Strengths Age.
Height sitting.
Span of arms.
Head.
Chest.
Waist.
lung capacity (hters).
5 6 7 8 The blood is freed from certain impurities, especially car- bon dioxide, by the lungs, where it is supplied with oxygen, which is the most immediate and imperative need of all crea- THE PSYCHOLOGY OF ADOLESCENCE tures that breathe. A deep instinct demands an abundance of free air space all about, and if this is limited, a peculiar class of fears, viz., of narrow or close places, being choked, dreams of being buried alive, and other acute panics, consti- tute a complete psychosis by themselves, v^^hich I have else- where described,^ may arise. The best age determination we have is still that of Gavarret for boys, in 1843, ^s follows: Age.
TI.
Gr.
5 Age. I6i.
Gr.
Age. Or.
The number of grams of carbon burned or exhaled from the lungs per hour depends largely upon the development of the muscular system. In girls Gavarret found it never to amount to quite seven grams per hour from the age of ten to forty-five, except at fifteen and nineteen in subjects with good muscles. This important difference between the sexes becomes much more marked at puberty, and menstruation may, as Marro suggests, tend to check this increment. From Scharling's table it would appear that while a girl of ten expires but 19. i grams of carbonic acid per hour, or 0.88 gram per kilo of weight, a girl of nineteen expires 25.3 grams, or 0.45 gram per kilo of weight. A boy of nine expires 20.3 grams, or 0.92 gram per kilo of weight, while one of sixteen expires 34.3, or 0.59 gram per kilo of weight. These very diverse results can not yet be coordinated.
Although the female organism needs less air than the male, and needs it less imperatively, and although the adult woman produces but little more than one-half the carbonic acid evolved in the male body, both have about the same temperature. The frequency of respiration in the two sexes, however, does not vary greatly, the difference being found in respiratory capacity. The chief pubertal change is from the abdominal characteristic of all children to the costal type, which girls assume during adolescence. This view, which has long been held to be a natural difference, has, however, been lately challenged by studies upon savages and peasant wom- en, which suggest that the difference may be due to corsets ^ A Study of Fears, p. 132, Sec. III. Fear of Closeness.
PARTS AND ORGANS DURING ADOLESCENCE 105 or tight lacing. That corseted mature women breathe more frequently than men is clear, but the difference in respiratory type due solely to age and sex is probably less than has been hitherto taught. Landois thinks that the vesicular murmur of respiration, which is somewhat raucous in early childhood, grows softer at puberty, owing to the widening of the pul- monary alveoli.
E. Growth of the Brain. — According to the tables of Vierordt, the brain increases between twofold and threefold in weight during the first year of life; not far from ten per cent more during the second; no less and a little more during the third. During the fourth year alone it increases more than it will during all the rest of life, and is nearly done growing by the sixth year. After eight it will grow but little, although the body has only one-third its mature weight.^ Increase, how- ever, continues very slowly till about twelve or fourteen years of age, when it about reaches its maximal size, although recent minute determinations by Mies and Pfister indicate a very slight growth to between twenty and thirty. In old age it gradually loses weight and size. In the average man it begins to decline by fifty-five, according to Bischoff, while in emi- nent men it may actually increase to sixty-five before the senescent shrinkage and atrophy begins. Individuals, no doubt, differ widely in this respect. The brain nearly fills the skull, more completely in women and children than in adult men. Cranial capacity, however, may continue to increase till the volume of the brain lacks from ten to twenty-five per cent of filling it. Thus at the beginning of school life the brain has