Paper - On the prenatal growth of the human body and the relative growth of the various organs and parts

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Jackson CM. On the prenatal growth of the human body and the relative growth of the various organs and parts. (1909) Amer. J Anat., 9(3): .

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This paper uses the measurement of weight as the main feature for "growth". Paper is in early draft edit stage.

See also: Jackson CM. On the developmental topography of the thoracic and abdominal viscera. (1909) Anat. Rec. 111: -396.

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On the Prenatal Growth of the Human Body and the Relative Growth of the various Organs and Parts

BY

C. M. Jackson.

From The Anatomical Laboratory, University Of Missouri, Columbia.

With 4 Figures And 6 Tables. THE AMERICAN JOURNAL OF ANATOMY.-—VOL. IX, N0. 1. 120 C. M. Jackson.

Introduction

Although numerous observations on various phases of the growth of the human embryo and fetus are scattered throughout the anatomical literature, they have never been collected and presented so as to give a comprehensive View of the subject. It is the purpose of this paper to present, in addition to the data already available, the results of an extensive series of original observations. These observations were made primarily in order to fill some of the eizisting gaps in our knowledge regarding this subject, particularly concerning the rate of growth during the earlier months. It is now possible to describe (though imperfectly and still subject to correction by further data) the general course of prenatal growth in the human body, and in its various organs and parts.


The material used for these observations includes 43 specimens from my collection of human embryos and fetuses. The specimens range all the way from 6 mm. up to the full—term fetus. Upon 32 of these specimens, the observations include the total volume, and the volume of the head, trunk, extremities, and of each of the principal organs of the body. For supplementary data concerning human embryos of the first month, the volumes of seven of the His-Ziegler models were measured.

For obvious reasons, the volume rather than the weight was chosen for measurement in the case of the models. In the small embryos also the volume may be determined, where it is diflicult or. impossible to ascertain the weight. Even where the organs are large enough to be dissected out and weighed, one does not like to sacrifice valuable specimens for this purpose, if it can be avoided. On the other hand, it is comparatively easy, though somewhat tedious, to measure the volumes of embryos which have been cut into serial sections. The sections must first be drawn to a definite scale of enlargement. Then one may proceed in either. of two ways. In the first embryo meas- ured (11 mm.) a rough model was constructed by Born’s wax—plate method, and the volumes of the body and of the various organs and parts were measured by water displacement.‘ An easier method,.

which is equally accurate, was used with other small embryos. In the enlarged drawings of the sections, the areas of the body and of

the various organs were measured by means of a planimeter. The-

volumes desired were then easily calculated by multiplying the areas. (corrected for magnification) by the thickness of the sections. From the third month onward, it was found possible to measure directly the volumes desired by means of water displacement in graduated’ glass cylinders of various sizes. In some fresh specimens the volume

and specific gravity were determined by weighing successively in air’

and suspended in water.

Certain sources of error must be recognized in the use of these-

methods. First is the effect of the reagents used. Most of the speci-

_ mens used had been fixed and preserved in 5 per cent to 10 per cent:

formalin solution. It is well known that in general formalin causes

a certain amount of swelling or expansion of tissues. In one fetus. of the 5th month in which this point was carefully observed, the-

swelling amounted to nearly 13 per cent of the total volume, after three months in a 10 per cent formalin solution. Furthermore, it is stated that the swelling is not equal in all of the various organs,

though the amount of difference and the conditions of occurrence are-

not yet fully known. Alcohol, on the other hand, causes shrinkage.

‘This embryo was studied by Bonnot and Seevers (6) under my direc- .

tion. I am also under obligations to J. A. Watkins, M. L. Clint, and R.

Lhamon for assistance in making a part of the observations used in this

paper.

For the specimens sectioned, it must also be remembered that the process of dehydration and embedding in paraffin causes a shrinkage of at least 20 per cent, or more than enough to counterbalance the swelling due to the formalin fixation. It is improbable, however, that the errors from these sources are large enough to affect materially the main conclusions concerning growth, especially concerning the relative growth of the various parts.

In the following pages there will be considered briefly : first the pre- natal growth of the body as a whole, then the relative growth of its principal parts, and finally the relative growth of most of the indi- vidual organs. For the organs and parts, it has been found more convenient and useful to record the relative size, expressed in per- centage" of the entire body. From these data, the absolute size of any part can easily be calculated, if desired (that of the whole body being given).

1. Growth of the Body as a Whole

In Table I, a list is given of the 43 specimens upon which my own observations were made. In the first column, the catalog numbers (in my collection) are indicated. In estimating the age of the speci- mens, Mall’s rule was used for the first four months and Hasse’s rule for the last five months. In the fifth month, a compromise was used between figures derived from Mall’s method and those from Hasse’s.

In Table II, some observations upon the volumes of the His-Ziegler models are recorded. The embryos corresponding to these models have been figured and described in detail by His (23), who gives no data concerning their weight or volume, however.

While a considerable amount of data has accumulated concerning the growth of the fetus from the 4th to the 10th month, very few observations have been made upon the earlier. embryos. In fact up to this time no data have been published which allow any accurate conclusions concerning growth in the human embryo during the first three months. My own observations include, in addition to the seven His—Ziegler models, eighteen embryos within this period. Two of these embryos (6 mm., 7.3 mm.) are of the 1st month, six of the 2d month; and ten of the 3d month. Four of these embryos (6 mm., 11 mm., 17 mm., and 31 were measured from sections, the remainder by the direct method described (7 .3 mm. by weighing).

The data obtained from these specimens form the basis for the figures givenfor the first three months in Table III. The volume of the human ovum (the diameter being assumed to be .2 mm., as usually stated) is about .000OO4 cc., which, assuming the specific gravity to be 1.0, corresponds to a weight of .0O00()4c g. The 7.3 mm. embryo (volume .026 cc.) was probably somewhat shrunken by the alcohol and embedding process so that the volume of .041 cc. obtained from the His model of a 7.5 mm. embryo is perhaps nearer the true size at the end of the first month, corresponding to a weight of about .04: g.

Thus we obtain for the relative monthly growth rate” of the 1st month, 9999; for'the 2d month, 7 4; for the 3d month, 11. Fehling (16), whose figures are often quoted, gave no estimate for the 1st month, but (without reliable data) estimated the relative monthly growth rate for the 2d, 3d, and 4th months at 3, 4, and 5 respect- ively, the greatest relative growth being in the 4th month. My ob- servations, however, prove beyond doubt the conclusion of Miihlmann (36), recently emphasized by Minot (34), that the relative growth in the human embryo is by far the greatest during the 1st month, declining rapidly at first, then more slowly hroughout succeeding months. ‘

Even the large number, 9999, representing an increase of nearly one million per cent, is in reality too small for the r.elative growth of the human embryo during the 1st month. For as a matter of fact, not the entire ovum, but only a portion of it, actually goes to form the embryo. The remainder is concerned with the formation of the membranes, etc. Since it is not known what proportion of the ovum goes for each of these purposes, the problem may be approached in another way. Table IIIa shows the weight of embryo plus mem- branes and enclosed fluids, at the end of the 1st, 2d and 3d months,

‘The relative growth rate is the ratio of the gain during a given period to the weight at the beginning of the period, and is the most accurate index of the rate of growth. It indicates the increase in a unit of weight during the given unit of time. Thus while the total amount of gain in absolute weight increases steadily for each prenatal month, the gain per gram of body weight (as shown by the relative growth rate) is constantly decreasing.

according to observations by Waldeyer (44) and Daflner (10). This gives the enormous figure of 574,999 for the relative growth during the 1st month, corresponding to an increase of over 57 million per

cent. This number is undoubtedly too high, however, since the fluids enclosed in the membranes and making up a considerable proportion of the total weight, can hardly be fairly considered as products of em- bryonic growth, in the ordinary sense of the term. The true relative growth for the 1st month therefore lies somewhere between 1 million and 50 million per cent.

From the foregoing, it appears that the relative growth of the human embryo is enormous in the 1st month, declining thereafter, at first very rapidly, then more and more slowly. The next question

Table 3

TABLE IIIa.

GROWTH on THE HUMAN EMBRYO PLUS MEMBRANES AND ENCLOSED FLUIDS. __,l_ . mm, ..., _ l . . . . ’ R 1 t" G th

Weight at Beginning 1 Weight at End  e éloivfiongfilv


of 12/gopth.  of l:’It§>i)xth.  (phi?)

hm, .._____ _. g _, ,__ 1st Month. (Ovum .oo00o4 g.) 2.3 g. (Wa1deyer.) 574999.

c J 2d “ l 2.3 g. | 25 g. (Daffnen) 9.9 3d " § 25 g. I 100 g. 3.9

which naturally arises concerns the growth within the 1st month. Some light is thrown upon this question by the observations on the volumes of the His models, recorded in Table II.

First it may be noted that the yolk sac is relatively large in the early embryos. In the 2 mm. embryo, it makes up more than three- fourths of the total volume. In the 2.6 mm. embryo, the yolk sac remains at about the same absolute size, but owing to the increase in the size of the embryo proper, it here forms less than two-thirds of the total volume. In my 6 mm. specimen (No. 176) the volume of the yolk sac was .0056 cc., forming a little more than one—third of the total volume, the embryo proper measuring .0098 cc. According to Mall (29) the diameter of the yolk sac is approximately 1 mm. at the age of 1 week, increasing 1 mm. each Week up to the 6th. It is therefore evident that although the growth of the yolk sac has been relatively very great during the first two weeks, its later growth is much less rapid.

As to the embryo proper, the actual volume at the end of the 2d week (2.2 is seen to be .O0O781 cc. As the volume of the ovum at the beginning is about .00O004L cc., this corresponds to an increase of 195 times in volume during the first half of the 1st month. During the second half of the 1st month, the embryo proper increases from .0007 81 to about .04 cc., or about 50 times. It is therefore evident that the growth of the human embryo is relatively more rapid during the first half of the first month than during the second half. The difference would appear still greater, if the growth of the yolk sac, membranes, etc., was taken into account.3

From what we know of the development in lower animals, as Donaldson (11) has pointed out, there is probably no increase in volume during the early segmentation stages of the ovum; so that the increase must be all the more rapid when it actually begins.

In addition to the observations in Tables I and IT, a considerable amount of data concerning the prenatal growth of the whole body from the 4th to the 10th months has already been published. Ahl- feld (1), Fehling (16), Legou (25), Faucon (15), Michaelis (35) and others have recorded the weight of fetuses whose age was es- timated from menstrual histories. Curves of absolute growth for the prenatal period, based upon these data, are shown in Fig. 1, (curves 1, 2, 4, 5). No curves are shown for the data of Faucon and others which do not difier materially from those given. From all the data available, I have ventured to construct a normal curve (Fig. 1, curve 3), which is intended to represent the absolute pre- natal growth, according to our present knowledge. As will be seen, it does not diifer greatly from that based upon the data of Fehling (who utilizes also observations from I-Iecker and Schroeder). Ahl- feld’s figures seem entirely too high for the average weight at the

“Daffner (10) gives the weight of a fresh “ovum” of fourteen days as 0.82 g., which is more than 200,000 times the weight of the ovum at the beginning. During the second half of the third month, however (accept- ing WaIdeyer’s observations of the 2.3 g. for the weight at the end of the first month), the embryo plus membranes, etc., increases only about three times in weight.


corresponding ages, in spite of his statement that “Nur solche Kinder verwendet werden deren Mutter den Tag der Conception genau an- zugeben wussten.” Hennig (19) has published a curve of growth in fetal weight, but without the data upon which it is based. His «curve shows a marked increase in the growth rate in the 6th and 8th months, followed by retardations in the 7th and 9th months. Donald- son (l2) believes that a new phase of growth in the human fetus begins with the 6th month, where the curve of absolute growth begins to rise more rapidly. A study of the growth rate, however, as ex- pressed by the figures for the relative monthly growth rate in Table III (or corresponding figures in Fehling’s table) reveals no evidence of any marked change at this particular time.

All of the data being considered, it seems most probable that the normal curve of fetal growth is fairly regular, though the uncertainty regarding the age of specimens and the degree of individual variation makes it very difiicult to determine this curve accurately. The curve

as drawn (curve 3, Fig. 1) is fairly regular, corresponding roughly -

to the formula y = X4, or

d Weight (g): 3(7 ays) 4

From this formula, the weight may be calculated approximately from the age, or vice versa, for any time beyond the first month. By some such growth formula the age should be determined more accu- rately than by the length (which theoretically should vary as the cube root of the volume, or weight) .4 The majority of previous "investigators have concluded that for determining the age, the length is a more reliable criterion than the weight; probably because the skeleton, which determines the length, is thought to be lessvariable than the soft parts, which make up most of the weight. This is still an open question, however. '

‘Roberts (40) has worked out a rule, assuming that the weight increases as the cube of the age; but this results in figures somewhat too high for "the average weight at the various months. This is also the case with the formula: Weight (g) = 50 (months — 2)’ recently proposed by Tuttle (42). 3250

3000 2750 -

2500


250 ,0 50 75 1_00 I25 I50 I75 200 225 250 275 Age in Days

FIG. 1. Curves of absolute prenatal growth. Cu . 1, data from - feld; 2, from Fehling; 4, from Legou; 5, from Mic ' . Curve No. 3 - sents the normal curve of growth (weight) cons ct the author, based on Tabl om all data available. he do esent the total body vol- ume in entimeters of the spe ' ens stu the age being estimated‘ from th


Although the growth rate at the end of the fetal period is far less than at the beginning, it is still very rapid as compared with the growth rate after birth. If the relative monthly growth rate of the last fetal month (.45) were maintained during the first year after birth, the weight of the body at the end of the first year would be over 250 kilograms! This marked diminution in the growth rate after birth indicates that the prenatal conditions are far more favorable to growth than the postnatal.

As may be seen by the dots in Fig. 1, the volume in’ cc. of the fetal specimens studied, the age being estimated from their length, cor- responds roughly to the curves of growth in weight, where the age was determined from menstrual history. We should expect the curve of growth in volume to differ slightly from that of weight, on account of slight changes in the specific gravity of the fetus. In the earlier months, the specific gravity of the embryo is very little over 1, though in later fetuses it reaches 1.04 or 1.05.

2. Relative Growth of the Principal Parts of the Body

Since growth is not uniform in the various parts of the body, these must be separately considered. No data have been published showing the relative size of the head, trunk and extremities in the various prenatal months, although it is Well known that the head is at first relatively large and the extremities small. My own observations on the relative growth of the various parts in 32 specimens ar.e included in Table IV. The relative size of the head was also observed in 5 of the His models (Table II).

The growth of the various parts in the specimens observed is illus- trated graphically by the curves of relative growth shown in Fig. 2.5

The unbroken lines connect points corresponding to the observations on the 32 specimens in Table IV. The dotted line at the beginning of the “Head” curve indicates approximately the relations found in the His models representing embryos in the latter part of the 1st month. The dotted lines on the right indicate, for convenience of comparison, the relative growth of the corresponding parts between birth and adult life, based chiefly upon observations by Meeh

‘It must be borne in mind that the curves of relative growth merely indicate whether the part is growing more or less rapidly than the average rate of the body as a whole, whose absolute growth curve is shown in Fig. 1.


The method followed in dividing the body was to separate the head from the trunk by a plane passing ust below the mandible anteriorly, and just below the cranium posteriorly. The neck is therefore included in the trunk. The upper extremities were separated from the trunk by an approximately sagittal plane through the shoulder joint, and the lower extremities by an oblique plane through the hip joint, parallel to Poupart’s ligament. As it is impossible to pass these planes always in exactly the same way, the measurements on difierent specimens are not exactly comparable to each other, though the error is comparatively small. There is also a certain loss of blood, etc., especially in the case of the fresh specimens.

Head

As may be see-n in Table 11, the head in the His models of embryos in the latter half of the 1st month forms from 34: per cent to 39 per cent of the entire body volume. Table IV and the “Head” curve in Fig. 2 show that the head reaches its maximum relative size, about 45 per cent of the total body volume, during the 2d month. There- after it declines gradually in relative size, forming only about 26 per cent or 27 per cent of the total body at birth.

His (23) from a study of the profile areas in embryos of the 1st and 2d months, concluded that the head is at first relatively small, increasing from about 30 per cent in the latter part of the 1st month to 56 per cent of the total body at the end of the 2d month. He thought that the head and trunk during this period are in a sort of race for supremacy, first one being larger, then the other. Profile areas, however, lacking the third dimension, are not necessarily in the same proportion as the volumes. His calculates the profile areas of the head in his embryos 4 mm., 5 mm. and 7.5 mm. to be 32.3 per cent, 30.7 per cent and 30.6 per cent of the total body; but I find in his models of these same embryos the Volume of the head to be respectively 34.9 per cent, 38.7 per cent and 36.6 per cent of the total volume. In no specimen examined by me does the head exceed the trunk in size, though it sometimes approaches it closely.

The steady decrease in the relative size of the head from the 2d month onward is in part due to a corresponding decrease in the relative size of the brain (which will be described later). As the brain throughout bears a fairly constant ratio to the volume of the head (somewhat less than half), however, it would appear that the facial portion of the head must also decrease in relative size at about the same rate as the brain. This does not agree with the conclusion of Merkel (82), who found the facial portion of the head of about the same relative size in a series of fetuses of different ages, excepting the youngest (3d month), where the face was relatively larger.

In the adult, according to Meeh’s (31) observations, the head forms from 6 per cent to 11 per cent of the total body volume; or,

according to Harless (18), 6 per cent to 9 per cent of the total body weight.

Trunk

In Fig. 2, the curve of the relative growth of the trunk is not repre- sented in the 1st month. Since, however, the extremities are very small at this time, it is evident that the trunk must be relatively very large. When the head forms 35 per cent of the body, the trunk would necessarily form nearly 65 per cent. At the beginning of the 2d month, as is shown by the curve, the trunk has decreased in relative size, so that it forms about 50 per cent of the total body volume. From the 2d month onward, the trunk continues to de- crease (somewhat irregularly) in ielative size. During the first half of the fetal period, the curve of relative growth of the trunk descends nearly parallel with that of the head. The curves diverge in the second half of the fetal period, however, that of the trunk remaining on the whole nearly horizontal, fluctuating between 40 per cent and 4-5_ per cent.

Meeh (31) separated the trunk from the lower extremities by a horizontal section at the level of the perineum, which apparently adds about 6 per cent to the relative size of the trunk. The average in 8 adults measured by him is about 54 per cent, which would correspond to approximately 48 per cent of the total volume by mg method. Between birth and adult life the trunk therefore apparentlg increases slightly in relative size.

Trunk

A- ,i ‘Nnu.. hank.

1


7

Lower Extremities

' II-If r’ 2--

5IIfl-_4m- WWW; in 3’

o __:._L|j

‘I40 180 200 220 240 260 280

DU

Days of Gestation

FIG. 2. Curves showing relative prenatal growth of the various parts of th< body, in specimens studied, the size being expressed in percentage of the tota body volume (Table IV). The dotted lines at the right represent the postnata growth of the Corresponding parts (based on data from Meeh).

The Extremities

The extremities are seen to be at first relatively very small, eacl forming between 2 per cent and 3 per cent of the total body volume during the 2d month. The upper extremities are usually slightly larger than the lower until early in the 3d month. Then both begii to increase in relative size, the lower more rapidly. The increase ii the relative size of the extremities during the first half of the feta period counterbalanoes the relative decrease of the head and trunl during that period, as shown by the curves in Fig. 2. In the second half of the fetal period, the extremities continue to increase in relative size, but more slowly; the increase of both counterbalancing the continued decrease in the relative size of the head, the trunk remaining nearly unchanged. At birth, the upper extremities form about 10. per cent of the whole body, the lower. about 20 per cent. In the adult (judging from the data of Meeh and Harless), the upper ex- tremities have increased but slightly, if at all; while the lower ex- tremities have increased to about 35 per cent, or nearly twice the relative size at birth.

In general, it may be said that the period of maximum relative growth passes somewhat wave—like over the body from the head toward the foot. The head, as we have seen, reaches its maximum relative size in the 2d month. In the trunk, the upper portion, including the thorax and the upper abdominal viscera, is relatively largest during the earlier half of the fetal life. The lower part of the ab- domen becomes more prominent toward the end of the fetal period, due chiefly to the rapid expansion of the intestines at this time. The pelvis and lower extremities do not reach their greatest relative size until early adult life, although the upper extremities have reached their maximum relative size at birth.

It may also be noted that the organs lying dorsal to the body axis (brain and spinal cord) grow at first far more rapidly than the organs ventral to the body axis. The volume of the brain and spinal cord together at the beginning of the 2d month is nearly 3 times as great as the combined volume of the organs lying ventral to the body axis. At birth, they are about equal. In the adult, the ventral organs are 6 times as large as the brain and spinal cord. The significance of the rapid growth of the brain and spinal cord in determining the marked flexure of the body in the early embryo has already been pointed out by Merkel (32) and by Keibel (Normentafel zur Ent- wicklungsgeschichte des Schweines, 1897

3. Growth of the Individual Organs

As the growth rate of the whole body is the resultant of the growth rate of the various parts, so the growth of the various parts depends in turn upon the growth of their component organs. The relative size of the principal organs in the specimens examined is given in Table IV. In Table V the average relative size of the principal organs is given for the various lunar months. In this table, all the available data published in the literature have been utilized, measurements on about 800 embryonic, fetal and newborn specimens being used.

T 2 ‘ “ 2"‘ "B K. 2° II ‘ I- ” fit 3' III -._ I0 ‘ ,. III_ 1 ' .» V 3 // V‘ S ‘:’ . -:j:__:— ,,__ ——- L \ 7'; ‘ K ..‘—‘j_ __n L my ~~—_ ‘~ ___ 1- 0 -— ‘E15.-;-.2-_22i__-5--__ D 2 3 4 5 6 7' 8 9 10 = 5 S 3 Lunar Months 55, %

FIG. 3. Curves showing relative prenatal growth (percentage of the total body weight) in the brain, spinal cord, liver, lungs and heart. Based upon Table V, from all data available, grouped by months. The dotted lines on the

left indicate probable relations of the first month, as explained in the text; those on the right connect the data for still—born with the corresponding

figures for live-born.

These include observations by Welcker and Brandt (45), Legou (25), Faucon (15), Arnovljevic (3), Brandt (8), Anderson (2), Boyd (7), Lomer (28), Meeh (31), Liman (26), Thoma (41), Oppen- heimer (38), Miihlmann (36), Collin and Lucien (9), and Beneke (4). A few cases, clearly either abnormal or erroneous, were exclu- ded. In calculating the averages in Table V, the percentage of the total body Weight) was reckoned separately for each specimen, then Prenatal Growth of the Human Body. 133

the average percentage taken for all the cases in each lunar. month. This is more accurate but more tedious than to divide the sum of the weights of an individual organ by the sum of the corresponding body weights. The latter method was used only in the case of the data by Boyd and Oppenheimer and the lung observations by Schmitt, Dever- gie and Elsasser (cited by Liman). In these cases, the individual data are not available, but the number of observations is so large that the probability of error is reduced. The figures in parenthesis fol-


Lunar Months

FIG. 4. Curves showing relative prenatal growth (percentage of total body weight) in the kidneys, suprarenal glands, spleen, thymus and thyroid gland. Based upon Table V, from all data available, grouped by months.

lowing the averages indicate the extremes of variation in relative size for the corresponding period. My own data (Table IV), in terms of volume (cc.) have been added unchanged to the others in terms of weight (g.), although strictly considered they are subject to a slight correction on this account.

‘In Figs. 3 and 4, curves are shown illustrating graphically the relative prenatal growth rate for some of the principal organs. Table VI shows the relative size of the various organs by lunar months, the

Live—born 134 r . C. M. Jackson.

sexes being separated, and also the right and left in the case of the

paired organs. Data from the literature were utilized here as in Table V.

The Brain

Although subject to considerable individual variation (of. Tables IV and V) the relative size of the brain, when the average for lunar months is taken (Table V), gives a fairly regular curve of growth, as shown in Fig. 3. No data for the 1st month are available, but it is very probable that, as in the case of the whole head, the maximum relative size is not reached until the 2d month. Then it is seen to form slightly more than 20 per cent of the entire body. From this time onward, it decreases in relative size. The increase at the 9th month is probably accidental, due to the small number of observations. The decrease is most rapid in the first half of the fetal per.iod, the relative size remaining fairly constant in the latter half, as noted by Legou, (25). The brain reaches an average of about 12.8 per cent in the still-born fetus (120 cases). In those born living, the average ap- pears to be somewhat higher, being about 14.6 per cent (90 cases). The reason for this increase in relative size in the live-born, which is found in all of the organs (excepting pancreas and suprarenal glands), is not clear. In the case of the lungs, it is evidently due chiefly to a larger influx of blood, and this may perhaps in part ac- count for the difference observed in the other organs.

After birth, as is well known, the decrease in the relative size of the brain continues, reaching about 2 per cent in the adult. Vierordt (43) gives an estimate of 12.29 per cent of the total body weight for the brain of the new-born, and 2.16 per cent for the adult. It may be noted, however, that Vierordt’s estimates (which are widely used) are not calculated from individual data, and are therefore not free from the possibility of error.

Spinal Card

The spinal cord attains its maximum relative size earlier than the brain. In an embryo of the fifth week (11 mm.), it forms 4.85 per cent of the entire body, and in models of earlier stages appears even larger. . As seen in Table IV and V, and also by the curve in Fig. 3, the spinal cord declines rapidly in relative size during the 2d and 3d months, then more slowly throughout the remainder of the fetal period. At birth, it forms only about .15 per cent of the entire body (average of five cases, including two of Bischoff). It is thus evident that the prenatal decline in relative size is more marked in the spinal cord than in the brain. In other words, prenatal growth is relatively more rapid in the brain than in the spinal cord, espe- cially in the earlier part of the fetal period. After birth, the relations are changed; so that the postnatal growth of the spinal cord is relatively more rapid than that of the brain, as pointed out by Donaldson (11) and Bonnot and Seevers Vierordt gives .18 per cent of the total body weight for the spinal cord in the newborn, and .06 per cent for the adult.

Eyeballs

As is well known, the eyeballs are relatively large at birth, forming, according to Vierordt, .24 per cent of the entire body weight, as compared to .02 per cent in the adult. Welcker and Brandt (45) cite 2 newborn in which the eyeballs formed .20 per cent and .38 per cent, respectively, of the entire body weight; in one fetus (6th month) they formed .71 per cent and in another (8d month), .53 per cent. I have made no systematic observations on the eyeballs, but in 3 fetuses of about the 6th month (Nos. 210, 211 and 218), the eyeballs were weighed and formed .45 per cent, .40 per cent and .39 per cent, respectively, of the entire body weight. It is thus evident that they are relatively largen in the fetus than at the birth; and they are probably still larger in the embryo.

Thyroid Gland

Although subject to considerable individual variation (cf. Tables IV and V) the thyroid gland in general increases slowly but steadily in relative size during the prenatal period, as shown by the curve in Fig. 4 (data from Table V). In an embryo of 2 months (3.1 cm.), it formed .035 per cent of the total body, increasing to .111 per cent 136 C. M. Jackson.

(average of 26 full—term still—born) or .125 per cent (average of 11 born alive). Vierordt gives .16 per cent of the total body weight

for the thyroid gland in the new—born, decreasing to .05 per cent in the adult.

Thymus

In the youngest specimen measured (end of 2d month), the thymus formed only .008 per cent of the entire body. As may be seen in Tables IV and V, it is subject to extreme fluctuations in relative size, being in this respect one of the most variable of all the organs. VVhen the average of a considerable number of specimens is taken, however, as shown by the curve in Fig. 4 (from data in Table V), the increase in the relative size of the thymus is evident. The average of all observations available gives .326 per cent out the total body for the thymus in 124 full-term still—born, and .313 per cent for 101 born alive. According to Vierordt, the thymus decreases from .26

per cent of total body weight in the newborn to .04 per cent in the adult.

Heart

In the early embryo, the heart is relatively large. In the youngest specimen directly measured (5th week, 11 mm.), the heart formed 8.64 per cent of the total body volume. On the His-Ziegler model of a 4 week embryo (A, 7.5 mm.), I have taken measurements from which the heart is estimated to form more than 5 per cent of the total body Volume (as indicated by the dotted line at the beginning of the curve of relative growth for the heart in Fig. From this curve, and from the data in Tables IV and V, it is evident that the heart decreases rapidly in relative size, dropping to .85 per cent in the 3d month. It continues fairly uniform in relative size from the 4th month onward, usually averaging between .7 per cent and .8 per cent for each month. In 165 full—term still-born the average was .70 per cent; and in 164 born alive it was .77 per cent. Ac- cording to the estimate of Vierordt, the heart forms .76 per. cent of the total weight in the newborn, and .46 per cent in the adult.

Lungs

The lungs (Fig. 3, Tables IV and V) are relatively small at first. They increase steadily in relative size, reaching at the maximum an average of 3.29 per cent of the total body Weight during the 4th month. From this time on, they decline slowly (with considerable variations) in relative size throughout the fetal period.“

In the full-term still—born (289 cases) the lungs averaged 1.71 per cent of the total body weight. In the live-born (202 cases) the average was 2.18 per cent, the difierence doubtless being due chiefly to the increased blood supply to the lungs when respiration begins.

When respiration begins, the lungs expand to two or three times their. original volume. It is doubtful, however, whether there is any postnatal increase in the relative weight of the lungs, excepting the immediate increase when respiration begins. Vierordt gives 1.75 per cent of the total body weight for the lungs in the newborn (still- born and 1.50 per cent for the adult. The adult lungs vary ex- ceedingly in air and blood content, however, so that it is very diffi- cult to determine their normal relative size (volume and weight).

As to the comparison between right and left lungs, His (24) found the anlage of the right lung larger than that of the left from the very beginning, and attributed it to the asymmetry of the heart and mesen— tery. In the youngest specimen observed by me (11 mm.), there was no appreciable difi’erence_ in size between the two lungs (Table IV). Thereafter, however, the right lung appeared constantly larger than the left, averaging about 20 per cent larger throughout the fetal period. In the newborn, the difference appeared somewhat larger, being 25 per cent to 30 per, The ratio between the right and the left lungiissubject toiconsiderable individual variation. It is, however, apparently not correlated‘ with any corresponding variation in the size of the heart or thymus, but varies independently of these.

In the adult, according to most of the text-books of anatomy, the right lung averages only 10 per cent larger than the left. Data compiled by Vierordt, however, show that this figure is open to question and that the ratio is quite variable. If the difference is due to the asymmetry -of the heart, we should naturally expect it to be less in the adult, where the heart is relatively smaller.

°Legou erroneously concluded that the lungs remain of about the same relative size throughout prenatal life. The remarkably large relative size of the lungs during the middle period of fetal life seems to have escaped all previous observers.


Liver

In the youngest specimen in which the liver was measured (11 mm. , Table IV), it formed 4.85 per cent of the total body volume. At the beginning in the 1st month it is of course relatively smaller. As indicated by the curve in Fig. 3 (Table V), it increases to its max- imum relative size during the 2d and 3d months. At this time individual specimens may reach 10 per cent (cf. Table IV and V), the average being about 7.5 per cent of the total body. During the 4th month, however, the liver. drops in relative size to an average of a little more than 5 per cent. This average is maintained through- out the succeeding fetal months, although there is considerable indi- vidual variation. In 145 full-term still-born cases, the average was 5.05 per cent; while in 101 live-born it was 5.23 per cent. Vierordt estimates that the liver forms 4.57 per cent of the total body weight in the new—born and 2.7 5 per cent in the adult.

Pancreas

The pancreas is at first relatively small (cf. Tables IV and V), forming in a specimen of the 6th week (1.7 cm.) .032 per cent of the entire body volumef’ From the 4th month onward, the pancreas remains fairly constant inrelative size, averaging about .1 per cent of the entire body. In 37 full-term still-born, the average Was .105 .per cent. In 90 born alive the average was .145 per cent of the total body weight. Vierordt gives .11 per cent of the total body weight for the pancreas in the newborn, and .15 per cent for the adult.

Spleen

As indicated by the curve of growth in Fig. 4 (also Tables 4 and

"The case recorded by Welcker (45), in which the pancreas formed .45 [per cent of the total body weight, is either erroneous or an abnormality. Prenatal Growth of the Human Body. 139

the spleen is at first relatively small, but increases slowly to an average of .176 per cent of the whole body in the 7th month. About this time it appears to increase rapidly in relative size, avcrsaging over .4 per cent in the 8th and 9th months. In the full—ter1n still- born (143 cases) the spleen averaged .32 per cent of the total body weight, and in the live—born (101 cases) .43 per cent. Vierordt gives .34 per cent of the total body weight for the spleen in the new—born. and .25 per cent for the adult. The fetal spleen, as in postnatal life, is subject to extreme individual variations in relative size.

Stomach and Intestines

Only a few observations upon the prenatal growth of the alimentary canal are available, chiefly (besides my own) those of Arnovljevic

and Brandt  The data upon stomach and intestines (in—

cluding mesentery) are included in Tables IV and V. The data for stomach and intestines in Tables IV and V include contents. No data are available for the empty stomach before the 4th month, but since the contents are usually slight at this time, the figures given for the stomach plus the contents are probably only a little larger than they would be for stomach alone. It seems that the empty stomach is relatively somewhat larger at an early period than later. It varies irregularly in relative size, the average per cent of the entire body in the different months varying from .16 per cent to .39 per cent. A larger series would doubtless give more uniform figures. The figures for stomach with contents are at first but little larger than those for the empty stomach; but in the later fetal months the contents (chiefly mucous) become relatively much larger in amount. In the full-term fetus the empty stomach averaged .20 per cent of the entire body weight (7 cases), while the stomach plus contents formed .49 per cent (8 cases).

The intestine is relatively small in the early embryo, not being at the 5th week very much larger than the stomach. It grows very rapidly, however, so that in the full-term fetus the weight of the in- testines (either filled or empty) averages more than six times that of the stomach. As in the case of the stomach, the contents of the intestine are at first small in amount, but increase gradually, amounting on the average in the full-term fetus to about twice the weight (or- volume) of the empty intestines (plus mesentery). Vierordt estimates that the (empty) stomach and intestine together form 2.1 per cent of the entire body weight in the newborn, which is considerably’

higher than the figures just given (1.23 plus .20 equals 1.43 per cent). For the adult he gives 2.06 per cent.

For the entire alimentary canal (empty), from the end of the pharynx to the anus, a few data are available. Welcker and Brandt (45) cite 4 observations; fetus 3 mo., 2.49 per cent of the total body weight; 6 mo., 3.01 per cent; newborn, 3.15 per cent, and 2.45 per- cent. Miihlmann obtained a much higher figure for the empty canal in 2 newborn,—6.7 per cent and 7 per cent respectively. In a series- extending through childhood up to the adult, he found the relative weight of the alimentary canal gradually diminishing to an average of about 3 per cent of the total body weight in the adult.

On account of swallowed air and accumulated gas, in addition to- the fecal contents, the volume occupied by the intestines in postnatal life is relatively much greater than in the full—term fetus,——on the average probably twice as great.

Kidneys and Wolfitcm Bodies

Beginning with the 2d month, the kidneys increase in relative size, at the first rapidly, then more slowly, together forming an average of about 1 per cent of the total body in the 7th month (Fig. 4, Tables IV and V). They apparently decrease slightly in relative size during the 8th and 9th months, and in the full—term still-born (144 cases) the average was only .82 per cent of the total body. In the live-born, however, the average (101 cases) was 1.05 per cent. Vierordt estimates for the kidneys in the newborn .75 per cent; and for the adult, .46 per cent.

When the right and left kidneys are compared in size (Tables IV and VI, it is evident that in the majority of cases the left kidney is slightly larger than the right. As shown in Table VI, this is true on the (average in both sexes for every month from the 2d onward, except the 2d (2 cases only), 7th (female cases), and 10th (stillborn).

In the adult, it is well known that the left kidney is larger than the right in the great majority of cases (of. data by Thoma). Beneke (4) from observations on only a few cases concluded that at birth the kidneys are approximately equal in size, no difference being appreciable until after the 3d month (postnatal). The data col- lected by me, however, demonstrate that the predominance of the left kidney extends back to the early embryonic months. As to the cause of the smaller size of the right kidney, it is probable that its growth is retarded by the greater pressure of the liver on the right side. This conclusion is strengthened by the fact that (as will be shown later) the right suprarenal gland is also usually smaller than the left.

The Wolfiian bodies are relatively large in the early embryo, form- ing .60 per cent of the total body volume in an embryo of the 5th week (11 mm.) , in which the renal anlages are just appearing. As the kidneys enlarge, the Wolfiian bodies become not only relatively but absolutely smaller, as shown by measurements on the following three specimens:

EMBRYO NO. ACTUAL VOLUME OF WOLFFIAN BODIES. % OF TOTAL BODY. 60 (1.1 cm.) ? .oo0734 cc. .601 58 (1.7 cm.) 3 .00055 f . 124 57 (3.1 cm.) ; .0o045 , .0212

Suprarenal Glands

As is evident in Fig. 4, the curve of growth of the suprarenal glands is quite different from that of the kidneys. During the 2d month, when they first become definitely outlined, the suprarenal glands form about .3 per cent of the total body volume (Tables IV and V). They increase rapidly to a maximum of about .46 per cent in the 3d month, decreasing steadily thereafter in relative size. In the full-term still—bo=rn, they form an average of .246 per cent of the total body weight (108 cases), and in the live—born .229 per cent (101 cases). Vierondt gives .23 per cent for the suprarenals in the newborn, and .01 per cent in the adult.

‘As in the case of the kidneys, the left suprarenal gland is usually larger than the right. As may be seen in Table VI, where right and left are given separately, the left averaged larger for both sexes in every month except the 2d, 4th (female), and 6th (female), in which the right averaged larger, and in the 3d month, in which they were equal.

For a comparison of the right and left suprarenal glands in the adult, I have been able to find no data; but suspect that the left will be found the larger here also.

Reproductive Organs

Only a few observations upon the prenatal sex glands are available. In addition to the data in Table IV, I find the testis in embryo No. 147 (2.3 cm.) to form .160 per cent of the total body volume; and in No. 122 (3.9 cm.) .057 per cent. Welcker. and Brandt (45) cite a case (3d mo.) in which the testis formed .10 per cent of the total body weight ; and another (6th mo.) in which it formed .06 per cent.

In an embryo of the 5th week (1.1 cm.), before the sex could be determined with certainty, the anlage of the sexual gland formed .085 per cent of the to-tal body volume. Beginning with the 2d month and extending up to the 10th mo., the relative size of the testis, in per cent of the entire body, forms the following series :— .16, .056, .10, .040, .045, .060, .080. In the female, from the 2d to the 7th mo., the series for the relative size of the ovary (per cent of entire body) is as follows :——.112, .036, .035, .026, .022.

In both sexes it therefore appears that the sexual gland is relatively larger in the embryo than in the later fetal stages, and that the testis is much larger than the ovary at corresponding stages. According to Vierordt, in the newborn the testis and ovary are about equal in size, forming .026 per cent of the entire body weight. For the adult he gives .080 per cent for the testis and .012 per cent for the ovary.

Skeleton, Musculature and Skin

While the skeleton, musculature and skin were not observed in the present investigation (except in one specimen), it is perhaps worthwhile to mention briefly the data available, which are presented in the following table :—

. l 3 i 1 J. T t : F t C v ' V Average Average Ii:,!Z1‘bI,r.15g_) NE 51150 j 6{}? Newborn Newborn | Newborn Adult

(vgelckery Gm mo_ (Bischoff) 1 (Bischofi) I, (Bischoff) 1 (Vierordt) I (Vierordt)


Body Weightnl 12.51 g. 400.8g. 491 g. i 2360.5 g. 2915. g. 3100. g.

I ! eezoog Skeleton and It i I ligaments... 4 2 7 i, 19.0 %, 20.57% 18.03 % I 16.0 %* 13.77% I 17.48% . 6- 5 . , =, Mus0ulature...lJ ° L 22.7r.%a 22.71% I 23.30 % , 24.03% 25.05% 43.4 % E 1 * ‘ skin..........! 8.39% I 1 [|{15.34% Subcutaneous I 12.9 %} 14.97 % ‘ 20.33% H ;,19.73% 17.77% _f_at......... 1 1 , __,L13_.91%_J


It therefore appears that in the fetus the skeleton forms a some- what larger percentage of the total body weight than later. The musculature, on the other. hand, increases in relative amount with age. The skin also increases, on account of the accumulation of subcutane- ous fat. In the adult, the skin, exclusive of subcutaneous tissue, forms only about 6 per cent of the entire body weight (average of 6 normal adults, by VVelcker and Brandt).

Variations According to Sex

In Table VI, the relative size of several organs in the various months, grouped according to sex, is shown. The columns “No.” give the number of cases (including my o-wn and those already recorded in the literature), while “per cent” indicates the percentage of the entire body (chiefly weight, except in my own cases). The average weight of the entire body in each group is given at the foot of each “per cent” column.

It will be noted that the average weight of the entire body is larger for the male in each month, excepting the 5th and 9th months. In the 9th month, the number of cases. (5) is too small to be significant, and the figures for the 5th month may be accidental. The conclusion is ther.efore evident that the male fetus is heavier than the female fetus of corresponding age throughout the fetal period. We know, of course, that this is true in the newborn. The conclusion that it is true for the entire fetal period is strengthened when it is remembered that the age of the fetuses observed was determined in some cases by their length, the same rule being used for. both sexes. Since the body length of the male at term averages greater than that of the female, the same thing is probably true for the fetus, at least in the later months. If allowance were made for this in grouping the fetuses by months, the difference in body weight between male and female would be even more pronounced.

In most of the viscera observed, on the other. hand, the organs are, as a rule, relatively heavier in the females This is the case with the brain, heart, liver, spleen and suprarenal glands; while the thy- mus, lungs and kidneys are usually relatively heavier in the male. For the other organs, insufiicient data are available.

The brain averages larger in the female in every month, excepting the 4th, 5th and 8th. No data are available for the female in the 9th month, however; and none for the male in the 2d. So that, after all, the preponderance of relative weight in favor of the female is but slight, and perhaps without significance.

In the thymus, the relative size averages greater in the male for every month recorded, except the 10th. Here the averages are equal for those born alive, but slightly larger for the female in the still- born.

The heart averages relatively larger in the male for the 4th, 8th and 9th months; equal in male and female for the 7 th; and is larger in the female for the remaining months. Here also the significance of the difference is questionable, though well marked in the newborn.

The lungs, both right and left, average relatively larger in the male, excepting in the 3d month (2 cases only), 9th month (no data for female), and 10th month. In the 10th month, the averages are nearly equal in the still—born, but are decidedly larger for. the female in the live-born.

The liver averages relatively larger in the female for every month from the 3d onward. The only exception is the 9th month, in which no data are available for the female.

“This general conclusion was reached by Loisel (27) from a study of Legou’s cases. The additional data now available do not confirm most of his conclusions, however.

The spleen averages relatively larger in the female for each month from the 4th onward, excepting the 4th and 9th, in which the male is larger and in the 9th, where data for the female are wanting.

The kidneys are almost constantly relatively heavier in the male. In the 4th month, however, the kidneys average larger in the female, and also in the full—term still—born (only 1 female). No data are available for the female in the 9th month.

The suprarenal glands, unlike the kidneys, are usually relatively larger in the female. The only exception is the 6th month, in which the left suprarenal only averaged larger in the male. No data are available for the 9th month, or for the female in the full—term still- born.

Comparison with other Species

A comparison of the growth in the human body with that in the lower animals should be of value in enabling us to judge as to which phenomena ar.e common to various animals (and therefore probably more fundamental in significance) and which are peculiar to the human species.

It is possible at present to make such a comparison only to a very limited extent, owing to the lack of data concerning growth in the lower animals, particularly prenatal growth.

We may consider first the rate of prenatal growth in the body as a whole. It is a matter. of common observation that in forms with eggs of the holoblastic type of cleavage there is during the early stages of segmentation a period during which the cells divide actively, with little or no increase in volume. In fishes and amphibia, this initial period is longer than in the higher vertebrates. In the frog embryo, Davenport (10 a) has shown that after hatching the growth rate in- creases up to the 10th day (with coincident increase in the percentage of water), after which it decreases rapidly. Even during the initial period, while the segmenting ovum as a whole remains nearly sta- tionary in size, the actual amount of protoplasm is increasing rapidly at the expense of the yolk material.

His (21) in 1868 concluded that the relative growth in the chick is greatest at the beginning, a conclusion supported to a certain extent by the observations of Falck (14) on the weight of the chick embryo at various stages. The data by Welcker (45) also indicate that in the chick the relative growth rate diminishes steadily from the 9th day of incubation to the time of hatching. As Minot (34) has pointed out, an inspection of Keibel’s Normentafeln also demonstrates the more rapid relative growth in the earlier embryonic stages. Fischel (17) states that this is likewisetrue for duck embryos. We may therefore conclude that in the bird embryo the relative growth rate is most rapid at the beginning, and decreases with age. Preyer (39) gives a curve of growth showing the increase in the weight of chick embryos, based on 42 observations by Potter Growth is far more rapid than in the human embryo of the same age, since the chick reaches 30 grams in weight within 21 days. But on account of the great individual variations a much larger series of observations is necessary before it is possible to construct an accurate curve of growth for comparison with that of the human embryo.

For mammalian embryos also, the data available are not very ex- tensive. Fehling (16) has shown that in r.abbit embryos from the 15th day onward the relative growth rate decreases, at first rapidly, then more slowly. Minot (34) has confirmed this result. For ear~ lier embryos apparently no data are available. As in the case of the chick, however, it is easy to show that the rate of growth is in general far more rapid in the rabbit embryo than in the human embryo of the same age. Assuming the diameter of the mature rabbit ovum to be .116 mm. (Marshall), its volume would be about .00O0008 cc., and its corresponding weight about .OO00008 g., or about one—fifth that of the human ovum. At the end of about 30 days, the rabbit embryo has reached full-term, with an average weight of 38.35 g. (Fehling), which is nearly 50 million times the weight of the ovum! In the same length of time, as we have seen, the human embryo has increased in size only about 10 thousand times. The human or ganism reaches finally a larger size than the rabbit or chick, in spite of the lower growth rate, because growth continues for a much longer period of time (Minot).9

“Curves of growth by Donaldson (12) show apparently a slower prenatal growth in the white rat than in man. But for these curves the body


The only other, mammalian form upon which specific data con- cerning prenatal growth are available (so far as I know) is the guinea pig. A few observations by Hensen (20) show that, in gen- eral, the relative growth is more rapid during the earlier stages (from 16th day) than in later fetuses. There are, however, some irregulari- ties and evidently great individual variations.

Concerning the relative size and growth of the various organs and parts in embryonic life, exact data are still scarce. Certain facts, however, are already generally known, or can be easily observed from specimens or published figures. In all vertebrates, from the fishes upward, the embryonic head is relatively large, especially in the earlier stages. There is considerable variation in the extent to which this is true in different forms, however. It appears most strikingly developed in the amniota; less so, as a rule, in amphibia and fishes. The head is perhaps relatively largest in the embryos of birds, where it may form more than half the entire body. Among mammals there is also variation in different species; e. g., the head of the pig embryo is relatively much smaller than that of the rabbit or human embryo.

The extremities in all forms appear relatively small in the embryo, gradually increasing to the relative size of the adult.

Correlated with the size of the head, we find the brain always relatively larger. in the vertebrate embryo. It is almost always largest at a comparatively early stage, diminishing thereafter in relative size throughout prenatal and postnatal life up to the adult stage. In the chick, a few observations are recorded by \Velcker and Brandt (45) indicating that at the 9th day of incubation the brain forms 28.2 per cent of the body; at the 10th day, about 14 per cent; 11th day, 13 per cent; 13th day, 9 per cent; 17th day, 5 per cent; newly hatched 3 per cent; adult, less than .5 per cent. Similarly in the dog, shrew, salamander and stickleback, observations indicate that the brain is relatively larger in the embryo or newborn than in the adult.

weight and span of life in man and white rat have been reduced to the same basis. The actual growth rate in the guinea pig and rabbit has been shown by Minot (33) to be about 25 times as great as in the human body. Oppel (37) points out that animals of greatly diverse adult size are much less different in size at corresponding early embryonal stages.



For the spinal cord, however, this rule is apparently not constant. In the chick and stickleback, the spinal cord in the adult diminishes in relative size; but in the shrew and (to a slight extent) in the dog, it apparently increases from newborn to adult.

The eyeballs are in all the animals just mentioned (excepting the salamander?) relatively smaller in the adult. In the chick embryo of the 11th day of incubation (Welclier and Brandt), the eyeballs form nearly 25 per cent of the entire body. In the newborn chick, they have decreased to about 3 per cent, and in the adult to .3 per cent or .4 per cent.

The thyroid and thymus glands in the dog and shrew appear. to remain of about the same relative weight in the adult as in the new- born. For the spleen, this applies to the chick as well as to the dog and shrew.

The heart appears relatively smaller in the adult stickleback, chick and dog; but larger in the salamander and shrew ( In the chick, dog and shrew, the lungs are relatively smaller in the adult than in the embryo or newborn.

The alimentary canal is relatively larger in the adult stickleback, dog and shrew; but smaller in the salamander and chick. The liver is relatively Ipuch smaller in the adult shrew, slightly smaller in the adult stickleback, chick and dog; but much larger in the adult sala- mander than in the embryo.

The kidneys appear relatively larger in the adult stickleback and salamander, but smaller in the shrew, dog and chick (slightly). The suprarenal glands are relatively slightly larger in the adult shrew, (no data on other forms). The reproductive glands are relatively larger in the adult chick, but smaller in the dog and shrew.

If we compare the foregoing data with the course of growth in the human body, two facts stand out clearly: In the first place, it is evident that, although the growth rate of the body as a whole varies greatly in different animals, it is greatest in the early embryo (at least in birds and mammals). In the second place, it is evident that in vertebrates in general the prenatal growth is relatively greater in the head region, including also individually the brain, eyeballs, and tongue.

Beyond this it is perhaps unsafe to generalize, on account of the scanty data available; but it seems likely that the viscera in general (c-irculatory, repiratory, alimentary and genito—urinary) are as a rule relatively smaller in the adult than in the earlier stages of the higher vertebrates. If this is true, it follows that the remainder of the body (chiefly locomotor apparatus) must be relatively greater in the adult, which appears to be true in the chick, dog and shrew, as well as in the human species.

Significance of the Growth Changes

It is the purpose of the present paper to present facts concerning growth, rather than to speculate upon their significance.“ It may be worth while, however, to point out that growth can be considered with reference to (1) its immediate causes, or its physiological, ontogenetic or phylogenetic significance. Concerning (2) we may safely say that the size of an organ or part, like its position, form, and structure, may depend upon, or be related to, the present, past and future. The present refers to the physiological relations which the part bears to the existing organism, an increase or decrease in function being generally correlated with a corresponding increase or decrease in size. The past refers to the conditions associated with the ontogenetic” or phylogenetic history (of e. g., Wolifian bodies) of the individual.

The future refers to changes in an organ which take place in anticipation of physiological needs which will arise at a later period in the life cycle of the organism. Preyer’s (39) statement that “Im embryonalen Leben diejenigen Theile am schnellsten wachsen welche

“The prenatal tongue is relatively larger in the chick, dog and shrew (Weicker and Brandt).

“For a detailed consideration of the principles of embryonic growth, cf. His (22).

"It is noted that, in general, organs which arise as infoldings (brain, spinal cord) are relatively large at the beginning and decrease later, while the con- verse is true of organs which arise as outgrowths (glands, lungs, etc.). 150 C. M. Jackson.

am friihesten nach der Greburt in Function treten” is an inexact expression of this relation.

If we attempt to go beyond these general relations and to analyze the phenomena of growth in order to determine the more direct and immediate factors, we meet with the greatest difficulties. The problem appears at present too complicated for solution. The con- ditions determining the growth rate of an organ or organism (aside from heat, light and other external factors») may, however, be traced back to the cells and grouped under two general headings: (1) speci- fic physico-chemical differences in the protoplasm, chiefly determined (in the beginning) by heredity, which afiect metabolism and thereby the growth rate; and (2) conditions within the organism which aflect the quality and quantity of available food and oxygen supply for the cells, or which affect the removal of their waste products of metabolism.

Concerning the first group, the intrinsic difierences in protoplasm, we know very little.“ The second group of conditions is more easily accessible to investigation, however, and we may expect that much light will be thrown upon this phase of the problem of growth by experimental methods.

Summary

The more important conclusions concerning prenatal growth may be summarized as follows :—

1. The human ovum increases more than 10,000 times in size during the 1st month, the embryo proper attaining a weight of about .04: g. The increase for the succeeding months (relative monthly growth rate) is expressed by the figures 74, 11, 1.75, .82, .67, .50, .47 and .45. The curve of absolute growth after the 1st month cor- responds approximately to the formula:

“The tissues of early embryos are known to be very rich in water, and it has been suggested that this may favor the chemical changes in the rapid growth characteristic of that period. The converse, however, is probably nearer the truth. Minot (34) believes that the relative abundance ‘of nuclear material at this period accounts for the greater intensity of growth and that the decreasing growth rate results from an increase in the amount and differ- entiation of the cytoplasm.

Weight (g) = (9152 Say?) '

2. The head attains its maximum relative size, about 45 per cent of the total body weight, during the 2d mo-nth, thereafter decreasing to about 26 per cent at birth. A relatively large embryonic head is characteristic for vertebrates in general.

3. The trunk is relatively larger in the 1st month (about 65 per cent of the whole body) decreasing to between 40 per cent and 45 per cent in the later fetal months.

4. The extremities increase gradually in relative size from the beginning, the upper extremities forming at birth about 10 per cent of the entire body, and the lower about 20 per cent.

5. The brain curve of relative growth is nearly parallel with that for the head, reaching a maximum of about 20 per cent in the 2d month and decreasing thereafter to an average of 13 per cent or. 14 per cent of the whole body at birth.

6. The spinal cord is relatively largest (about 5 per cent of the entire body) in the 1st month, decreasing at first rapidly, then more slowly to about .15 per cent at birth.

7. The curve of relative growth of the heart is close to that of the spinal cord during the 1st, 2d and 3d months, remaining near an average of .7 per cent thereafter.

8. The liver increases to a maximum of 7.5 per cent (average) of the entire body during the 2d and 3d months, remaining fairly constant between 5 per cent and 6 per cent during the remainder of the fetal period.

9. The lungs increase gradually in relative size to a maximum average of about 3.3 per cent in the 4th (month, decreasing thereafter to an average of about 2 per cent of the entire body at birth.

10. The spleen, thymus and thyroid gland increase from the be- ginning more or less regularly in relative size, averaging about .4 per cent, .3 per cent, and .12 per cent, respectively, of the total body weight at birth.

11. The kidneys increase at first rapidly, then more slowly to a maximum of about 1.0 per cent in the 7th month. Later they decrease slightly in relative size, but average 1.05 per cent in the live- born.

12. The suprarenal glands increase rapidly to a maximum relative size of about .45 per cent of the Whole body in the 3d month, de- creasing steadily thereafter to about .24 per cent at birth.

13. In the case of the paired organs, the larger size of the right lung, left kidney and left suprarenal gland is established early in the fetal period.

14. At full—term, almost all of the viscera (excepting the thymus and suprarenal glands) average relatively greater in the live-born than in the still—born.

15. The fetal viscera appear as a rule to be relatively heavier in the female (excepting the thymus, lungs and kidneys).

Literature

1. AHLFELD, FR. Bestimmungen der Grosse und des Alters der Frucht vor der Geburt. Archiv f. GynEik., Bd. II, 1871, S. 353-372.

AivrmRs0N, A. Contribution of Facts to the Weights of the Fcetal Vis- cera. London and Edinburgh Monthly Jour. Med. Sc, Vol. IV. 1844, pp. 100-103.

3. ARNOVLJEVIC, S. Das Alter, die Griissen u. Gewichtsbestimmungen der Foetalorgane, Dissert, Miinchen, 1884.

4. BENEKE, F. W. Die anatomischen Grundlagen der Constitutionsanomalien des Menschen. Marburg, 1878.

5. Brscnorr, E. Zeitschr. f. rat. Med. 1863 (cited by Welcker and Brandt.)

6. BONNOT, E., AND SEEVERS, R. On the structure of a Human Embryo» Eleven Millimeters in Length. Anat. Anz., Bd. XXIX, 1906, S. 452459.

7. Born, R0131‘. Tables of the Weights of the Human Body and Internal Organs, etc. Phil. Trans. Royal Soc. London, Vol. 151, Part I, 1861.

8. BRANDT, E. Das Alter, die Grtissen u. Gewichtsbestimmungen der F0etal~ organe. Dissert. Miinchen, 1886.

9. COLLIN, R., ET LUCIEN, M. Sur l’evolution preponderale du thymus chez. Ie foetus et chez l’enfant. Bib}. Anat., T. XV, 1906, p. 24-38.

10. DAFFNER, FR. Das Wachstum des Menschen, Leipzig, 1897, (2d. ed., 1902).

10a. DAVENPORT, C. B. Experimental Morphology, New York, 1899. 11. DoNALDsoN, H. H. The Growth of the Brain, London, 1895.

12. TA Comparison of the White Rat with Man in Respect to the Growth of the Entire Body. Boas Memorial Volume, New York, 1906.

FALCK, C. PH. Beitréige zur Kenntniss der Wachsturnsgeschiclite des Thierkorpers. Archiv f. path. Anat., Bd. 7, 1854, S. 37-75.

————Beitr§ige zur Kenntniss der Bildung und Wachstuinsgeschichte der Thierkiirper. Schr. d. Ges. z. Befiird. d. ges. Naturw. zu Marburg, VIII, 1857, S. 165-249 (cited by Preyer).

FAUCON, A. Pesées et Mensurations foetales a differents ages de la grossesse. These, Paris, 1897.

FEHLING, I-1. Beitriige zur Physiologie des placentaren Stoffverkehres, Archiv f. Gyni‘Lk., Bd. 11, 1877.

FISCHEL, A. Ueber Variabilitétt und Wachstum des embryonalen Kor- pers. Morphol. Jabrb., Bd. XXIV, 1896.

HARLESS. Lehrbuch d. plastischen Anat-oinie, 2 Aufl., 1876 (cited by Vierordt). »

HENNIG. Die Wachstumsverh'2iltnisse der Frucht und ihre wichtigsten Organe, etc. Arch. f. Gynak., 1879.

HENSEN, V. Die Physiologie der Zeugung in Hermann’s Handbuch der Physiologie, Bd. 6, II Theil, Leipzig, 1881.

HIS, W. Untersuchungen iiber die erste Anlage des Wirbeltierleibes, Leipzig, 1868.

—Unsere Ktirperform, Leipzig, 1874. ———Anatomie menschlicher Embryonen, Leipzig, 1880-1885.

——Zur Bildungsgeschichte der Lungen beim menschlichen Embryo. Arch. 1:’. Anat. u. Pl1ysio1., Anat. Abt., 1887.

LEGOU, E. Quelques considerations sur le Developpement du Faetus. These, Paris, 1903.

LIMAN, C. Pract. Handb. d. gerichtl. Medizin Von Casper, 5 Aufl., Bd. II, Berlin, 1871. (Incl. data by Devergie, Schmitt, and Elsasser.)

LOISEL, G. Croissance comparée en poids et en longeur des foetus male et femelle dans Pespece humaine. C. R. Soc.'de Biol. Paris, 1903, p. 1235 ff.

LOMER. Ueber Gewiehtsbestimmungen der einzelnen Organe Neugeb0r- ener. Zeitschr. f. Geburtsh. u. Gyni_ik., Bd. XVI, 1889.

Mall FP. Normal plates of the development of vertebrates. Anat. Rec, (1908). MALL, F P., A Study of the Causes Underlying the Origin of Human Monsters. Journal of Morphology, Vol. XIX, No. 1, 1908.

MARSHALL, A. M. Vertebrate Embryology, New York and London, 1893.

MEEH, C. Volummessungen des menschlichen K61-pers und seiner einzelnen Theile in den verschiedenen Altersstufen. Zeitschr. f. Biol., Bd. 31, S. 125-147, 1895.

MERKEL, FR. Mensehliche Embryonen verschiedenen Alters auf Median- schnitten untersucht. Gottingen, 1894.

M1No'r, C. S., senescence and Rejuvenation. 1891. éThe Problem of Age, Growth and Death. New York, 1908.Jour. Physiol., Vol. XII, 154


MICHAELIS, P. Altersbestimmung menschlicher Embryonen. Archiv f. Gynak, Bd. 78, 1906.

Mi'IHLMANN, M., Ueber die Ursache des Alters. Wiesbaden, 1900. (Data

concerning Alimentary Canal also published in Archiv f. path. Anat., Bd. 163, and Anat. Anz., Bd. 18, 1900.

OPPEL, A., Vergleichung des Entwicklungsgrades der Organe zu ver- schiedenen Entwicklungszeiten bei Wirbeltieren, Jena, 1891.

OPPENHEIMER, C. Ueber die Wachstumsverhaltnisse des K61-pers und der Organe. Zeitschr. f. Biol., Bd. 25, 1889.

PBEYER, W». Specielle Physiologie des Embryo, Leipzig, 1885.

ROBERTS, R. C. On the uniform lineal growth of the human foetus. Lancet, CLXX, Vol. I, 1906, p. 295.

THOMA, R. Untersuchungen fiber die Grtisse und das Gewicht der anat. Bestandtheile des menschl. Kijrpers, etc., Leipzig, 1882.

TUTTLE, L. The Relation between Weight and Age in the Fetus. Amer. Med. Assn, Vol. LI, p. 919, 1908.

VIERORDT, H. Anatomische, physiologische und physikalische Daten und Tabellen. 3 Aufl., Jena, 1906.9

WALDEYER, W. Anatomische Untersuchung eines menschlichen Embryo, 28-30 Tagen. Studien d. Physiol. Inst. Breslau, 1865, S. 55 ff.

VVELCKEB, H., and BRANDT, A. Gewichtswerte der Korperorgane bei dem Menschen und den Tieren. Archiv f. Anthropol., Bd. XXVIII, 1903.


TABLE I. MEASUREMENTS OF SPECIMENS OBSERVED.

Catalog

Length in cm.

I E1\h§|)l)r;f) Sex Crown— lgagséé Volume. ' 1 Rump_ Total. I 1 1 1 u

176 — 0.6 cm.l _ 25

220 1 — ‘ 0.73 ~ I 27 1 .026 60 1 - I 1.1 — ‘ 33 1 .0976 58 1 f. 1 1.7 — 41 1 .3788 147 m. 123 ~ 1 48 1.3 99 1 f. 2.6 —— 51 1 3.0 224 ; - 1 3.0 — 55 1 2.29 57 f. 3.1 — 56 1 1.693 158 1 — ‘ 3.5 v 1 59 = 5.6 51 1 m. 3.5 ~ — 1 59 1 6.0 122 m. ’3.9 1 —- 1 62 f 4.1 185 1 — 14.5 1 6 5 ' 67 1 8.8 121 1 m. :46 — 68 1 5.0 115 1 m. 5.0 — 1 71 1 10.0 194 1 1. 5.6 1 — 75 ; 14.75 148 ‘ m. 5.8 —— 76 ; 15.5 197 f. 6.2 9.0 79 . 15.5 123 m. 6.8 9.2 1 82 . 24. 128 1 1. 7.5 j 12. 1 87 1 54 181 1 m. 9. 1 13.7 95 1 80 129 E m. 9.5 1 14.5 97 1 108 130 I f. 10.5 L 16. 1 105 1 122 143 m. 11. I —— 110 1 95 162 , m. 11.5 — 1 115 1 97 186 1 m. 113. 20.3 1 13011 243 199 1 f. 13.2 23. ’ 132 1 257 191 1 f. 14. 22.5 ' 140 1 370 211 f m. 15. 21.5 140 1 180 218 1 m. 15.5 23. 146 214 195 m. 16. 25.5 152 ‘ 375 154 1 f. 17. 26. 158‘ 464 210 1. 17.5 26.5 1 160 1 383 172 * m. 18. 27.5 1 165 460

89 f. .20. 3 28.5 1 170 605 171 1 m. 121. 1 31. . 174 1 690 192 1. 20. 1 33. 185 1 775 219 1 1. 23. 1 34. A 192 1 791 193 1 m. 26. 37. j 209 ’ 941 208 m. 31.5 46. = 258 1 1981 201 1 m. 30. 46.5 1 260 ‘2310 234 m. 31. 49. 1 274 2727 202 m. 32. ~ 50. ' 280 , 3470 198 m. 36. : 54. 302 1 3830

.O1544 cc.

Fixation.

Formalin. Alcoho1—Formalin. Alcohol. Formalin.

I I Alcohol—F0rmalin. Fresh. Formalin. Alcohol.

Formalin. (I

U H U (1 It U

(1

Alcohol. ({

I { l { Formalin. ( { l . I K I K Fresh. K ( Formalin . Alcohol. Fresh.

Formalin. C (

ll

H

Fresh. Formalin. Fresh. Formalin. Fresh. Form alin .


TABLE II. OBSERVATIONS ON VOLUME OF HIS-ZIEGLER MODELS.

_ .___ ‘ l _ - Number. 1 1(SR.)

4(M.) ;3(BB.) 5(Lr.) 6(a.) 7(11) 8(A.) ' 1 .12

Embryo length. 1 2.2mm. 2.6 mm.13.2 mm. 4.2 mm. 4 mm. 5 mm. 17.5 min.

Age His: 14 da. ; . . . . 1 20.da. .... 23 da. . . . .. 1 Mal1’s . ; 1 g 1 Rule... . .1 15 da. f 16 da. 1 18 da. 1 20 da. 20 da. 1 22 da. 3 28 da. Total volume of; 1 : 1 model.. . . .1 208 cc. 1 236 cc. 1 *95cc. *218 cc. 86cc. 1 124 cc. 1 328cc. Magnification ; v ; of model.... H40 diam. 140 diam. 40 diam. 1 40 diam. 20 diam. 20 diam. 20 diam. Corresponding 1 5 V 1

(actual) V 01- 1 1

ume of em-‘ 1 1

bryo . . . . . . . .0O325cc1.003687cc1.001484cc‘.0O3406cc.01075 cc. .0155 cc.: .041 cc.

Actual Volume_1 1 _‘ I

of embryo} 1

proper . . . . . . .1.000781CC;.001281C<3;0014:8400 .003406cc .01075 cc. .0155 cc. .041 cc. Actual Vo1ume1 1 of yolk sac.....{.002469cc..002406cc1 Head = % of 1

Total body.....; ‘_37.9%i } 33.9% 34.9%fi1__3s.7_f7;, 36.6%

1 1 1 1 1

  • In Nos. 3 and 5, the data of the volume of the models are somewhat uncertain

since in each a portion of the ventral body wall is deficient in the model. Cor- rection was made for this by adding 5 cc. to the volume observed for No. 3, and 9 cc. to that for No. 5.

TABLE III. PRENATAL GROWTH or‘ HUMAN Bony BY MONTHS.

1 1 - LuwMonth- 1 We;5h1.:;.%?%;s;11.. 1 31952111? 31:; 13333:? 1 . _.., _ 1 __ _ . . _ 2 -_- .. __ 1. 000004 g. .04 g. 9999. 11. .04 . 3.0 74. 111. 3.0 1 36 11. IV. 36. : 120. 2.33 V. 120. 1 330. 1.75 VI. ’ 330. 1 600. .32 VII. . 600. g 1000. . 67 VIII. 1 1000. * 1500 . .50 IX. 1 1500. 1 2200. .47 X. 1 2200. 1 3200 .45 1


TABLE IV. RELATIVE SIZE OF VARIOUS FETAL ORGANS


(IN PERGENTAGE OF TOTAL Bony VOLUME) IN S1>Ec11vfENs OBSERVED. No. and Sex. 60 (/3 58 (f) 57 (f) 185 (f) 1 148 (m) 197 (f) m.,_- _ _ ._!_.1 _. _ :_ ._ . '_._. ._, _.l _ Crown-rump length 1 1 1 cm 1.7 cm. 3.1 cm. 4.5 cm. 1 5.80111. 6. 2 cm. Volume of body . . . . .122 cc .4735 cc. 2.117 cc. 8.8 cc. 15.5cc. 15.5 cc. 1 l - .

Head . . . . . . . . . . . . .. .44.42% 45.76% 45.4% 143.18% 41.94% 36.8 <70 Upper extremities 2.91 2.13 2.64 4.67 i 5.87 5.75 Lower extremities 2.43 2.26 2.21 5.68 , 7.61 6.58 'Trunk................50.12 49.86 49.76 ;46.47 144.58 50.9 Brain . . . . . . . . . . . . .. 20.26 22.35 18.81 i 22.72 1 18.58

Spinal cord . . . . . . . . . 3 4.85 3.43 1.53 2 1.25 " .774

Thyroid gland . . . . . . .035

Thymus . . . . . . . . . . .008 - Hear:...............§ 3.64 1.71 1.32 1.14 ! 1.06 ‘ 103 Right lung ....... . . .18 .276 .777 1.7 E 1.26 1.74 Left lung . . . . . . . . .. ' .18 .21 .605 1.48 1 1.03 1.23 Liver . . . . . . . . . . . . .. ‘ 4.85 6.91 10.56 I. 7.39 6.45 8.71 Spleen . . . . . . . . . . . . . .019 ., .0088

Pancreas . . . . . . . . . .. .032 .0533 I Right kidney ..... .. ‘ .044 .115 g .255 3 .516 .29 Left kidney . . . . . . . .042 .105 ; .255 i .548 .355 Right suprarenal < .169 .141 .255 1 .31 .258 Left suprarenal . . .. . ._., .172 .131 .255 .31 .258 Stomach .......... .. ‘ .56 .17 . .452 .58 Intestines ......... .. .72 1 2.05 ; 2.0 2.71 Sex glands . . . . . . . . . .0852 .112 .0357 1 ' '

NOTE. To correct for shrinkage in the first three embryos (which were em-

bedded in paraffin), 25 per cent was added to the observed body volumes given in

Table I. 158

TABLE IV (Continued).

RELATIVE SIZE 01“ VARIOUS FETAL ORGANS (IN PERCENTAGE or TOTAL Bony VOLUME) IN SPECIMENS OBSERVED.

1

No. and Sex. 123 (m) 128 (f) l 181 (In) E 129 (m) 130 (f) 143 (In) 1""’”’ ’ ‘ ’“' "’ 5 "— " Crown-rump length ‘ 6.8 cm. 7.5 cm. 1 9 cm. 9.5 10.5 cm. 11. cm. Volume of body.... .. 24. cc. - 54. cc. 1 80. cc. 108 cc. 1 122 cc. 95. cc. 1 , 1

Head . . . . . . . . . . . . . ..143.75%‘40.74%140. % 39 81% 139.35% 40. % Upper extremities....1 4.17 1 6.11 1 6.88 6.02 ' 5.33 6.11 Lower extremities...‘ 6.25 10.2 1 9.75 . 9.07 - 9.43 8.42 Trunk...............‘ 45.83 142.96 143.38 _45.09 145.9 45.47 Brain . . . . . . . . . . . . . ..‘ 15.0 120.37 ’ 12.5 118.52 ‘ 21.31 20.95 Spinal cord . . . . . . . . .458 1 .278 1 .25 1 .14 ‘ .164 .21 Thyroid gland . . . . . 1 .11 % .063 .083 .102 f .095 Thymus . . . . . . . . . . . . .5 . . . . = . 1 S .075 .102 .148 .105 Heart ............. .833 1 .926 ; 1.125 1.39 I 1.19 .842 Right lung..........‘ 1.21 f 2.96 1 1.63 2.13 1 1.07 i 1.58 Left lung . . . . . . . . . 1.00 1 2.22 g 1.44 1.85 1 .82 1 1.16 Liver . . . . . . . . . . . . . 7.08 5.56 1 5.25 7.04 ’ 7.38 ; 5.05 Spleen . . . . . . . . . . . . 1 .056 .081 .074 .131 j .053 Pancreas . . . . . . . . . . .. .11 1 .094 . .102 ~ .123 1 .095 Right kidney ...... ..1 .292 1 .377 1 .4 i .46 1 .475 .295 Left kidney . . . . . . . .271 1 .35 } .369 - .509 .484 1 .316 Right suprarenal. . . . . .188 .17 1 .288 .204 ‘ .295 § .158 Left suprarenal . . . . . .188 .15 1 .275 .204 1 .344 .168 Stomach ........... .375 3 .33 : .25 .26 ' .41 .21 Intestines . . . . . . . . . . . .. 2.29 1 2. 78 1.0 ‘ 3.33 3 .36 1 2.84 Sex glands . . . . . . . . 1 5

TABLE IV (Continued).

RELATIVE SIZE OF VARIOUS FETAL ORGANS (IN PERCENTAGE OF TOTAL BODY

VOLUME) IN SPECIMENS OBSERVED.

No. and Sex.

Crown—rump length

i I

186(m) § 199 (f) ! ‘

211 (m)  218 (In)

.\ ‘

162 (m) 191 (f)


11.5cm. 13cm. 13 cm. 14cm. ‘:15.0cm.l15.5cm.

Volume of body.... . . 97 cc. 243 cc. 290 cc. 370 cc. 180.4cc.’ 214 cc. Head . . . . . . . . . . . . . .. 40.21% 39.5 % 37.93% g 39.19% 1 38.83% 40.32% Upper extremities.... 6.19 6.67 1 7.93 5 8.3 6.71 1 7.24 Lower excremitiee... 9.79 10.7 _ 13.79 ? 14.05 * 11.14 ; 12.13 Trunk............... 43.81 543.13 340.34 138.46 45.12 ;(42.) Brain . . . . . . . . . . . . . 18.56 913.16 213.79 E 16.22 16.94 i 16.29 Spinal cord ........ .. .263 .198 .203 E .232 .336 f .235 Thyroid giand ..... .. .052 .045 ' .062 1 .132 .080 1 .053 Thymus............. .103 3 .09 .107 g .243 .125 g .117

.618 1 .76 .876 1 .89 .67  .67

Right lung ........ .. 1.85 i 1.23 ; 1.07 .1 1.54 1.60 i 1.32 Left lung ......... 1.57 1.07 j .872 1.30 1.25 | 1.08 Liver . . . . . . . . . . . . . ..i 4.95 4.01 3.28 5.76 6.30 ' 4.70 Spleen . . . . . . . . . . . . .052 .07 .1 , .26 .077 l .095 Pancreas . . . . . . . . . . .. .103 .082 .107 I .108 .058 I .118 Right kidney........: .34 .33 . .35 I .62 .413 ‘ .58 Left kidney . . . . . . . .36 .41 .379 1 .73 .401 .57 Right suprarena1.....% .154 .164 E .19 1 .216 .224 \ .18 Left suprarenal . . . . ... .206 .185 .224 I .27 .247 .188 Stomach ........... ..i .32 .206 i .328 .405 .28 I .96 Intestines .......... ..i 2.58 2.18 - 3.1 3.05 2.86 1 2.68 sex glands . . . . . . . . — .035 g (.040) (.045)


TABLE IV (Continued).

RELATIVE SIZE OF VARIOUS FETAL ORGANS (IN PERCENTAGE OF TOTAL BODY VOLUME) IN SPECIMENS OBSERVED.

No. and Sex. 1 195 (m) 154 (f) 210 (f) 1 172 (m) 89 (f) E 192 (f) Crown—rump length . .1 16 cm. 17 cm. 17.5 0111.1 18 cm. 20 cm. 20 cm Volume of body . . . . . 375 cc. 464 cc. 1‘ 383 CC. I‘ 460 cc. 605 cc. 1 775 cc

«.4 1 7 — N 1 I ————— ‘ — Head . . . . . . . . . . , . . 37.33% 38.79% !37.13% 38.04% I 34.05% 1 37.42% Upper eXtremities....§ 8.53 7.76 1 7.91 7.39 I 8.1 l 8.0 Lower eXt1‘en1ities....1 15.28 13.36 1 13.81 14.78 ' 13.72 1 14.19 Trunk...............138.86 40.04 |41.07 139.78 144.13 140.65 Brain . . . . . . . . . . . . . .1 15.47 15.95 13.76 15.54 g 16.53 ‘ 16.65 Spinal cord ........ .. .187 .155 .226 I .184 .198 ‘ .271 Thyroid gland . . . . . .. .053 .069 .061 .148 .107 .132 Thymus . . . . . . . . . . . .. .2 _ .179 .171 3 .113 .165 .232 Heart . . . . . . . . . . . . . .. 1.07 ‘ 1.08 .83 ; 1.195 1.37 1.42 Right 1ung ......... .5, 1.27 1.25 1.59 1 .37 1.12 1.61 Left lung . . . . . . . . . . 1.04 1.08 1.42 1 .71 .88 1 1.2 Liver . . . . . . . . . . . . . ..f 5.87 4.74 5.81 5.4 6.94 6.19 Spleen . . . . . . . . . . . . .. .051 .11‘ .106 .076 .088 i .194 Pancreas . . . . . . . . . . .. .107 .097 .068 .098 .099 . .101 Right kidney..... . .. .427 .302 .378 .54 .446 1 .465 Left kidney . . . . . . . . .. .453 .28 .386 .51 7 .479 1 .490 Right; suprarenal. . . . . .373 .172 .154 .196 1 .182 .155 Left suprarenal . . . . . . . .400 .205 .186 .217 ‘ . 198 .232 Stomach......... . .28 .194 .52 .196 .529 .606 Intestines............ 2.59 3.02 2.34 2.83 3.8 4.26

Sex glands . . . . . . . . . .

1 (.026)


TABLE IV (Continued).

RELATIVE SIZE OF VARIOUS FETAL ORGANS (IN PERCENTAGE 01‘ TOTAL BODY VOLUME) IN SPECIMENS OBS-ERVED.

No. and Sex. § 171 (m) 219 (1)

r l

Crown—rump K

lengt;h.... . . . 21 cm. 23 cm. Volume of body . . . . . . .." 680 cc.j791.8cc.

3 K W 1 Head..........;33.09%§ 33.0 % Upper extrem- I 5

ities ....... 6.91 3 8.20 Lower extrem— ll 1

ities. .. .. . . . 15.15 15.32 Trunk.........I44.85 144.0 Brain ........ ..l 17.65 1 (16.0) Spinal cord... .199 1 .230 Thyroid gland .072 1 .043 Thymus ..... . .221 § .256 Heart . . . . . . . . 1.03 .87 Right lung .... . 1.4 9 1.36 Left 1ung.......§ 1.1 1 1.03 Liver ........ ..? 4.85 4.74 ‘Spleen . . . . . . . .. .078 l .227 Pancreas . . . . . . .074 .060 Right kidney.. .338 5 .468 Left kidney... .368 1 .484 Right supra-1-

renal... . . . . .‘ .147 I .136 Left supra-

renal . . . . . . .. .176 .160 Stomach . . . . . . .22 .519 Intestines .... ..: 3.24 1 3.77 Sex glands..... § (.022)

193 (In) 208 (In) 201 (m) 234 (m)

’ " 13*:

E 26 cm. 31.5 cm. 1 30 cm. 31 cm. 1 1 941 cc. 11981.4 cc.j231O cc. 2727.1 (:0. W. gn WT’ _... _..-__. . ".2 31.88%[ 30.9 % 31.86% 25.8 % 7.95 9.56 5 9.52 10.18 A 1 18.17 . 17.56 17.49 20.16 42.0 2 41.40 41.13 40.12 14.88 1 14.5 7 13.91 13.12 .191 ’; V .143 .084 .065 ; .065 .054 .425 1 .311 1 .212 .66 1.06 : .779 1.08 .59 1.51 : .988 ; .909 1.16 .79 ' .688 . . . . 6.38 4.35 2.0 4.84 .159 . .201 0 .108 .24 .069 [L .067 .054 .12 .499 } 885 .286 .37 .478 ’ .26 1 .41 .117 l [ g .087 .118 .231 4 .128 J [5 .087 .138 .213 . A .273 } 282 { 3,08 = 3.98 ‘ ’ .080 3 A


101

202(m) 198 (m)

1 E 135cm. 36cm. l3470 cc. 3830 cc. 1., _,,,_.,1.__ ’27.09% 26.9 %

9.65 15.14

519.31 19.84 143.95 44.12 111.10 9.48 .075 .091 i .110 .065 .320 .149 .72 .778 1 .576 I 4.61 V .188 1 sun. .231 . .228 I i l 1 5 TABLE V.—RELATIVE S1213 on FETAL ORGANS IN THE Vzuuons MONTHS.

Brain. . . . . Spinal cord . . . . Thyroid gland . . . Thymus . . . Heart . L . . . Lungs . . . . . Liver. . . . . . Spleen . .. . . Pancreas... Stomach (empty). Stomach (+ con- tents). .. Intestines (empty). Intestines (+ con- tents). . . Kidneys . . . Supra.- renals, . .

Avg. body Weight . .

No.

I-1

v-lv-*COCO¢‘0C\l(N

SECOND Mama.

% of Total Body.

20.47 (18.81—22.35)

3.27 (1534.85) .035 .008

2.22 (1.3213.64) .743 (.36-1.38)

7.44 (4.85—10.56)

.014 (009-019) .043 (.032—.053)

..u...

.56

.72 . 153 (.086—2.20)

.306 (.272—.341)

.904 g.

Tmnn MONTH.

No. % of Total Body.

5 19.15 (15.—22.72)

4 .82 (458-125)

.19

.85 (.55—l.14) 2.52 (1.36—3.18) 7.61 (5.—10.5)

4 .39 (.17—.56)

2.26 (2.—2.71) .659 (.46—1.06)

fill!)

5 .453 (.27—.62)

7 14.96g.

No.

30

28 38 37

.39

33

36

30

38

FOURTH MONTH.

% of Total Body.

15.72 (10.—23.7) .21 (.14-.278) .091 (.063—.11) .134 (,039~.41) .685 (40-139)

3.29 (1 .55—5.18)

5.08 (2.7—8.1) .092 (.02-.46) .105 (.063—.1l)

.25 (.23—.27)

.33 (.21—.46) 1.33 (1.2-1.45) 2.55 (1.—3.36)

.815 (.40—2.33)

.43 (.20—] .46)

FIFTH MONTH.

No.

53 13. 96 (9.58—23.03)

4 ~ . 25 (.198'-.263)

4 .073 (.052—.132)

50 .149 (.053-.41) 60 .65 (34-133)

61 3.09 (1.70—5.14) 59 3 5.27 (3.28-7.93) 52 . .107 (.O35—.26)

4 .100 (.082—.108)

4 .29 (.17~.45)

8 .42 (.21—.65)

4 1.24 (.58—1.67)

8 2.57 (2.—3.1)

60 .891 (.53-2.81)

49 .362 (.175-.86

234 g.

% of Total Body.

No.

49

45 63 1 64 . 64 60

10

10 64

44

67

SIXTH MONTH.

% of Total Body.

14.30 (933-203) .22 (.155—.336) .094 (.053—.143) .175 (.0 41-39) .73 (.45~1.37)

2.54 (1.28—4.16)

5.39 (2.68—8.69) .142 (.051—.36) .094 (.068—.107)

.29 (.19—.45)

.45 (.19—.96) .75 (43-10) 2.68 (1.96—3.14) .854 (.49-1.29)

.36 (.13—.773)

413.1 g. Brain . . . . . Spinal cord . . . Thyroid gland . . Thymus . . Heart . . . . Lungs . . . . Liver . . . . . Spleen . . . . Pancreas . . Stomach (empty) Stomach . . (+ con- tents) . . Intestines (empty) I11testines (+ con- tents) . . Kidneys . . Supra- renals . .

Avg. body weight . .

I 1 1 2

TABLE V (Continued).—RnLAT1vn SIZE on FETAL ORGANS IN mm VARIOUS MONTHS.

SEVENTH MONTH.

No. % of Total Body.

26 13.77 (10.94-17.65)

3 .23 (.199—.271)

4 .089 (.043—.132) 1 19 .285 (11-42) 3 36 .83 (.48—1.45) 36 2.58 (.98—6.31) 36 5.31 (3.39—7.8) 32 .176 (.043~.51) 4 .084 (.06—.101)

8 .39 (.22-259)

12 .51 (.22—.65)

8 1.27 (.85~2.30)

12 3.08 (1.69-1.26) 35 .987 (.47—2.13)

17 .31. (.143—.44)

.37 748 g.


.57

No.

65

58

68

EIGHTH MONTH.

% of Total Body.

12.46 (11.69—15.5)*'

.19 .129 (.055—.22) .259 (.10—.65)* .71 (.60—1.13)*

2.40 (1.39—3.45)*

5.28 (2.56—7.8)* .428 (.039—.44)* .129 (....)*

.25 (.17—.49)

.40 (21-82) 1.38 (.83—2.0) 3.35 (174-455)

.93 (.40—1.30)*

.28 (.17—.458)*

1196 g.


I

'1 1 4‘ 1


No.

{-16

NINTH MONTH.

% of Total Body.

14.48 (12.73—15.7)

.24 (.20—.36) .78 (.40-1.56)

2.14 (1.63—3.51)

4.93 (3.8—6.67)

.44 (.26-.74)

.16 (13-20)

.30 (.26—.37)

.98 (.65—1.5)

3 .36 (3 .O2—3 .52) ‘

.77 (43-107)

1609 g. '

1N0. 1120

5

26: 124 165 289 145 143-

8


» i 8: 1445

108i

1

i177?

TENTH MONTH. (Stil1—bom.)

9 I

% of Total Body. ' I I

No. 90,

12.78 (9.23—16.1)* . .144 (.075—.21)

.111 (.041—.33) _ .326 (.149—1.21)*‘_ .70 (.45—1.21)* . 1.71 (.061—3.49)* .9 5.05 (2.0—6.85)* .32 (.108—.73)* .105 (.067—.15)*


.20 (.14—.23)


.49 (.26—1.39) 1.23 (.77—1.75) 3 . 53 (2.78—3.76‘)

.82 (.40—1.49)*

.246 (.11—.52)*

3046 g.


TENTH MONTH. (Live-born.)

% of Total Body.

14.59 (....)*

.125 (.089—.16) .313 (.141—.53)* .77 (.45—1.44)* 2.18 (1.02—3.65)* 5.23 (3.03—7.48)* .431 (.08—.39)* .145 (. . . .)*

....

1.05 (i.-85—1.83)*

.229 (.11—.36)*

2590 g.

  • IndividuaI variations not available in Boyd's cases, which include 48 in the 8th month, 83 in the 10th month (still-born), and 90 in the 10th month (live-born);

in 0ppenheimer's 23 cases (10 month, still-born), and in 155 observations on the lungs (10th month) by Schmitt, Devergie and Elsasser.



TABLE VI. RELATIVE SIZE OF FETAL ORGANS IM THE VARIOUS MONTHS BY SEXES.

I THIRD MONTH. , FOURTH MONTH. ‘ FIFTH MONTH. SIXTH MONTH.

g SECOND MONTH.

. . I . Male. ' Female. Male. Female. Male. Female. ! . .

Female.


1 l



. Per Cent

Cent No. Per Cent . Per Cent No. Per Cent

No.


15.15 26 14.40 2313.58 14.33

.135: 24 .150 22 .140 . I .169

.704 30 .638|24 .675 137 .70 $25 .78 1.71 24 1.53 36; 1.44 :25 1.32 1.47 1.30 1361‘ 1.21 125 1.08 . 5.16 :25 5.29 38; 5.34 25 5.46 .073 26 .1o7122 .108 36? .136 23 .150 .388 30 .439 24 .439 37! .425 25 .420 .405 29 .473 A25 .443 37. .429 25 .424 .287 124 .154~’21 .177 21: .179 21 .181 .2683 24 .173 ;22 .189 201 .192 22 .178

226 g. 25 253 g. 405 418g. 25 402 g.


Brain.............. .. 2120.52 ;31 . 122.72 15 15.41 Thymus . . . . . . . . . . .. .. 5 15 .00017g 1 I .. 13 .151 Hea.rt.............. .. 52' 1.51 ‘ 3 1 09 . 15 .74 Rightlung . . . . _ . . . ... .53 I 2 1.72 16 1.80 Left lung......_... ‘ .41 2‘ 1.36 16 1.50 Liver . . . . . . . . . . . . .. .. 3 805 16 5.47 Spleen... . . . . . . . . .. ... 15 .107 Rightkidney........ .. .273 16 .384 Leftkidney.........' .. .305 16 .386 Rt. suprarena1....—..j .. .257 14 .191 Lt. suprarenal ..... ..; .257 14 .197

I106.2 g.


l"1I—1 COCO com cow V—(V—1

3

oo

<6

I‘(

c c\1’NrNc.~1c\1"c\1<.\xc\1

00 (N 65 O ©

Av’gebodyweight..:.._ 2; 1.4g. 15 3§17.34g. 2j12.15g. 16 1 1 1| 1 4


TABLE VI (Continued).

RELATIVE SIZE OF FETAL ORGANS IN THE VARIOUS MONTHS BY SEXES.


TENTH MONTH.

TENTH MoNTH. (Live—born.)

NINTH MONTH. (stflbboml)

z 1' SEVENTH MONTH. ; EIGHTH MONTH.



Female. ‘f Male. Female. . Male.


T 1 No.;Per CentI\No. 1 i


No.

7 Ml Per Cent'N0_. Per Cent

Brain 15113.32 _11 14.37 Thymus . . . . . . . . .. 101 .290’ 9; .279 Heart . . . . . . . . . . .. 20} .83 16? 83


24|12.24 ; 14.48I.. 71 12.91 .253 23} .224;. 1 ._: i65 .296 .7 251 .69 .83 4. .81 .80} .69 Right lung'........ 20; 1.43 :16. .30 251.29 1.33 ..§ .69‘ .98 Left lung . . . . . . . .. 20; 1.25 316 1.07 - .15 25; 1.07 ’ 99 .. f69 .79 Liver . . . . . . . . . . . .. 20i 5.05 T16: 5.64 '34: .21 I25," 5.55 1 . .. ;71 4.81 Spleen. . . . . . . .....17i .19115' .158 404125] .5241 70 .27 Rightkidncy. ' 16 .453; .517 5} .441 ’ Left kidney 19 .535 161 .4412

Rt. sup1'arena1..... 9 .139 8 .166

I .367 .520 53 .456 . . .. .341 1 .130 2 .174 .. .. Lt. suprarenal . . . 9 .148 81 .170 '-

.101 .154 2 .176 .. .. Av’ge body weight. 21 833 g.|16‘ 637 g.


O>O3C\1C\l CD 03 Q V?‘ V‘ -lDCOC'JO'DC“DC‘O€"J O 0'3 113 5: V-'(


89; 3067 g. 645 2963 g. 74. 2725 g.i79] 2464 g.

.111

1 .1 .__.. 1.. 5 1526 g.: 5 '



Cite this page: Hill, M.A. (2019, October 17) Embryology Paper - On the prenatal growth of the human body and the relative growth of the various organs and parts. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/Paper_-_On_the_prenatal_growth_of_the_human_body_and_the_relative_growth_of_the_various_organs_and_parts

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