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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.

{{Ref-Mall1908}}
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 '



{{Footer}}
[[Category:Draft]]