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The prenatal growth of the cat. III. The growth in length of the two extremities and of their parts

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THE PRENATAL GROWTH O F THE CAT
111. THE GROWTH I N LENGTH O F T H E TWO EXTREMITIES AND O F
T H E I R PARTS
HOMER B. LATIMER
University of Eansas
FOUR FIGURES
The linear growth of the fore limb, the hind limb, and the
three major divisions of each appendage will be presented
in this paper. All of the measurements were made on the
fore limbs of the 264 specimens, but in nine of the smallest
fetuses the hind limbs were so poorly developed that only
the length of the entire extremity could be determined accurately. All of the measurements of the hind limb were made
on the remaining 255 specimens.
The four extremities were removed, as described in the first
paper of this series, f o r weighing the entire extremity. After
weighing, the following measurements were made. All measurements were made and recorded for both the right and
the left sides, and the average of the two is meant whenever
it is not otherwise stated. The arm was measured from the
head of the humerus to the tip of the elbow. Next, the length
from the tip of the elbow to the tip of the toes was measured.
The length of the forefoot was measured from the tip of
the toes to the dermal pad on the ulnar side of the wrist.
This pad, according to Reighard and Jennings ( ' O l ) , marks
the location of the pisiform bone, and it seemed to be the
best external landmark for separating the forefoot from
the forearm. In a few of the smallest specimens there was a
second smaller pad proximal to this pad. The difference
between these last two measurements gives the length of the
forearm, and the sum of the shoulder-elbow and the elbow-toe
377
378
HOMER B. LATIMER
measurements gives the total length of the fore limb. These
specimens had been formalin hardened, so that it was very
difficult to straighten the appendages to make a direct measurement of the total length, and so this method is more accurate than a direct measurement of the total limb length.
The hind limb was measured in a similar manner. The
length of the thigh was measured from the proximal part of
the head of the femur to the patella. The second measurement was made from the patella to the tip of the toes, and
the third was the length of the foot from the tip of the longest
toe to the proximal side of the calcaneus. The total length
of the limb was the sum of the first two measurements and
the length of the leg is the difference between the second and
the third measurements. The hind limbs were more easily
and more accurately removed from the body, but the fore
limbs were easier to measure accurately. The hintlfoot was
flexed on the leg very frequently, so that it was hard to get
the knee-toe measurement accurately, and it will be shown
later that the leg length is the most variable dimension in
this series of measurements. The foot was gently but firmly
straightened in making the knee-toe measurement.
The author wishes to gratefully acknowledge the assistance
of Dr. John M. Aikman in making the measurements on the
first 137 specimens.
FORE LIMBS
The lengths of the fore limb and of its three segments
plotted on body length (nose-anus) are shown in figure 1.
The dots represent the average length of the two fore limbs
of the males, and the circles the average of the two limbs
of the females. The distribution of the cases for the lengths
of the arm, forearm, and forefoot is very similar to that
for the fore limb, with no apparent sex difference jn any of
the measurements, and so only the curves for the three segments are shown in t,his figure. This facilitates the comparison of the relative lengths of the parts and of the entire
appendage.
PRENATAL GROWTH O F THE CAT
379
The empirical formulae from which all four curves were
drawn are:
Fore limb,
Y = 0.453 X - 7.6
Arm,
Y = 0.1735 X - 3.2
Forearm,
P = 0.16 X - 3.3
Y = 0.119 X - 1.3
Forefoot,
I n all of these formulae Y represents the length of the part
measured in millimeters, and X the body, or nose-anus, length
also measured in millimeters, and plotted as the abscissae in
the figure. All of these formulae are valid between 30 and
200 mm. of body length. The four curves of absolute growth
Fig. 1 The growth of the fore limb plotted on body length in the upper curve
with the dots representing the males, and the circles, the females. Curves are
shown f o r the three segments, but the individual cases are not given. The
values for the percentage curve are in the left margin, although marked ‘mni.’
The formulae f o r the four curves of linear growth are given i n the text.
are all straight-line curves, or they exhibit a constant rate of
increase throughout this period.
The curve in this figure marked ‘percentage’ represents
the total length of the fore limb expressed as a percentage
of the body length. The figures in the left margin marked
‘millimeters’ serve not only to show the actual lengths, but
also the percentages for this curve. On the preliminary
chart all of the individual percentages were plotted and a line
was then drawn through the averages for each 10 mm. in-
380
HOMER B. LATIMER
crease in body length, and this line only was transferred to
this figure. The distribution of the percentages about this
line was fully as close as the cases about the curve in figure 1.
This curve shows that the length of the fore limb increases
from about 20 per cent of the body length to slightly over
40 per cent, or the length of the fore limb grows about twice
as fast as the body length during the fetal period.
Fig. 2 The growth of the fore limb and its segments plotted on body weight.
The upper curve gives the total length with the dots representing the males,
and the circles, the females. The individual cases are not shown for the three
segments of the appendage. Formulae f o r all four curves are given in the text.
The ordinates in the left margin, although marked ‘inni.,’ give the correct values
f o r the percentage curve.
Figure 1 and the computed lengths show that the forefoot
is the longest part of the fore limb in the smallest specimeiis.
It is surpassed first in length by the arm a t 40 mm. of body
length, and at a body length of 50 mm. and over it is the
shortest of the three divisions. The entire fore limb increases about 14 times. The forefoot increases a little less
than 10 times, the arm about 16 times, and the forearm about
19 times.
Figure 2 shows the lengths in millimeters of the fore limbs
and the three parts plotted on body weight in grams. The
upper curve with the dots representing the males and the
PRENATAL GROWTH O F THE CAT
381
circles the females shows the linear growth of the fore limb.
The lower three curves represent the linear growth of the
arm, forearm, and forefoot, and, as in the preceding figure,
the cases for these are not included in this figure. The curve
marked ‘percentage’ represents the average percentage of
the length of the fore limb of the nose-anus length plotted
on body weight. It was drawn in a manner similar to the
curve in figure 1. The distribution of the cases on the preliminary chart is possibly a little closer in this case, especially
for the larger specimens. The figures in the left margin
serve for percentage values for this curve as well as millimeters for the curves of linear growth.
It is interesting to note that in the formulae for the linear
growth of the fore limb and for its three parts and likewise,
as will be shown later, f o r the hind limb and its three segments, the increase in length is a function of the cube root
of the body weight. The formulae from which the four curves
in this figure are drawn are:
Fore limb,
Arm,
Forearm,
Forefoot,
Y = 14.5 VX-
Qx
Y = 5.8
- 0.015 X
Y = 5.2 9-r-0.5
Y =4 V X
I n all of these formulae Y represents the length of the extremity or its part measured in millimeters, and X, the body
weight in grams from 1to 200 gm. of body weight.
A comparison of the distribution of the cases in the curve
of the fore limb in this figure and in figure 1 shows that there
is a massing of the cases at the beginning of the curve in
this figure, while in figure 1, the cases are crowded toward
the end of the curve. I n other words, the body length increases more rapidly at first than the body weight, as has
been shown in figure 1 of the first paper of this series. The
curve representing the growth of the forefoot does not cross
the other two curves as it did in figure 1. This is due to
this crowding of the cases at first and also because these
formulae begin at 1gm. of body weight, which excludes many
of the smaller specimens. The formulae will not fit the cases
below 1gm. The curves in figure 1 are more accurate for the
smaller specimens.
382
HOMER B. LATIMER
The percentage increments of the fore limb, and of its
parts computed 011 body weight are larger a t first and decrease
to smaller values than the corresponding increments computed for body lengths. This is as would be expected, since
the linear dimensions increase more rapidly at first than the
weight .
T o derive the empirical formulae in this and the preceding
papers of this series, the dimensions were plotted on a field
graph; next, the average of the dimension and of the abscissa
were determined f o r each 10-gm. increase in weight or each
10-mm. increase in body length. h smooth curve was drawn
through as many of these average points as possible and an
empirical formula developed to fit the curve. The formula
was solved for each 10 units of the abscissa and plotted on
the final chart, and through these points the final curve was
drawn. To give an idea of the accuracy with which these
curves in figures 1and 2 and also in the two following figures
fit the cases, the difference between the observed length and
the calculated length for each 10 mm. or 10 gm. increase in
the abscissae was determined. The table giving the average
linear differences for each curve and also the average percentage differences for each curve is omitted. The curve for
the forearm plotted on body length has the greatest average
percentage difference (5.04), and it is the only one of the six
curves f o r the fore limbs which has a percentage difference
exceeding 5 per cent. All three curves plotted on body length
are not as well fitted to the cases as the three plotted on body
weight. The smallest percentage difference of 1.65 per cent
is found in the curve of fore limb length on body weight.
The cat fetus resembles the human fetus in the straight-line
curves of the upper extremity and its parts plotted on body
length as given by Scammon and Calkins ('29) and others,
and the increasing percentage of the body length resembles
the changes in the percentages of the human upper extremity.
The percentage values given by Scammon and Calkins ('29)
are not comparable with the percentages given here, f o r these
percentages are based on nose-anus length, and not crown-
PRENATAL GROWTH OF THE CAT
383
rump or crown-heel lengths. No attempt will be made to
discuss the rather extensive literature on the growth of the
linear dimensions of the extremities of the human fetus, for
this has been so well done by Scammon and Calkins ( '29).
Schultz ( ' 2 6 ) finds a decrease in the growth of the human
extremities in relation to the trunk height from the sixth t o
the tenth fetal month and similar changes in apes and monkeys. The first part of his percentage curve rises as do the
Fig. 3 Growth of the hind limb and its segments plotted on body length is
shown in the upper curve. The dots represent males, and the circles, females.
The individual cases are not shown for the three segments of the extremity.
Formulae for the four curves are given in the text. The ordinates in the left
margin give the values for the percentage curve as well as for the other curves.
percentage curves for the cat extremities. His curve rises
more rapidly at first and the dip toward the end is much
more pronounced than in the cat fetus. I n general, the linear
growth of the fore limbs of the cat fetus resembles that found
in man and monkeys.
HIND LIMBS
The linear growth of the entire hind limb plotted on body
length is shown in the upper curve in figure 3. The individual dimensions are shown as dots for the males and circles
for the females. The three lowest, curves, with the individual
384
HOMER B. LATIMER
cases omitted, represent the growth in length of the three
parts of the hind limb. The formulae for all four curves are
given below.
Hind limb,
Thigh,
Leg,
Rindfoot,
Y = 0.458 X - 9.74, from 30 t o 190 mm. of body length
Y = 0.165 X - 4.025, from 35 t o 200 mm. of body length
Y = 0.1 X - 2.1, from 36 to 190 mm. of body length
Y = 0.186 X - 3.70, from 36 t o 190 mm. of body length
I n all of these formulae Y represents the length of the limb,
or its part, in millimeters, and X, the body length (nose-anus)
also measured in millimeters. The formulae for the parts of
the extremity begin at either 35 or 36 mm. of body length,
for, as has been previously stated, the hind limbs of the smallest specimens were not sufficiently developed to permit the
measurement of the parts of the appendage with any degree
of accuracy. This slower development of the hind limb as
well as its shorter length and lighter weight (Latimer and
Aikman, '31) illustrates the law of developmental direction.
The distribution of the cases for the hind limb, the leg,
and the hindfoot differs from the lengths of the other extremity and the other parts plotted on body length in that
these dimensions in the newborn cats are longer and so are
above the curve drawn for the fetuses. I n figure 3 all of
the cases above 71 mm. of length represent the length of the
hind limb of newborn cats. This greater length is apparent
in the preliminary charts for the growth of the leg and of the
hindfoot, but not for the thigh. This increase in the lengths
of these dimensions is not quite as evident when the body
weights are used as abscissae. I n figure 4 the cases between
121 and 160 gm. of body weight are newborn cats, and they
show a rather sudden increase over the lengths of the fetuses
just less than 121 gm. of body weight. All of the fetuses
weighed 121 gm. or less. A possible explanation of this increase is the straightening of the ankle joint at birth. It has
been stated above that it was difficultt o straighten this joint in
the fetuses in order to get good measurements of these parts.
This would explain the increase in the leg and the entire
extremity, but it is not a satisfactory explanation for this
increase in the foot length.
PRENATAL GROWTH OF THE CAT
385
The percentage curve in this figure represents the lengths
of the hind limbs reduced to percentages of the body lengths.
The figures in the left margin represent the percentage values
as well as millimeters of length. Thus the hind limb forms
but about 10 per cent of the body length at first and increases
to a little over 40 per cent There is a marked similarity
between this curve and the percentage curve of the fore limb
shown in figure 1. The greatest difference is at first, for the
fore limb starts with about twice the percentage length of
the hind limb. This is due, of course, to the more precocious
development of the fore limb.
The foot is the longest segment of each extremity at firsi.
It has been shown that the forefoot is rather quickly surpassed in length by the other two segments of the fore limb,
but it will be seen from figure 3 that the hindfoot remains
the longest segment of the hind limb throughout the entire
fetal period and also in the newborn. The leg is the shortest
part and the thigh intermediate throughout the entire period.
Using the computed lengths of the two extremities and their
parts, it is readily seen that the entire hind limb as well as
each of its parts is shorter at first and increases more in the
fetal period than the fore limb or the corresponding parts of
the fore limb. The hind limb increases 20.4 times in length,
or nearly one and a half times the similar increase of the fore
limb. The thigh increases more than any of the other parts
or the two extremities. It increases over 31 times, or nearly
twice the increase of the arm. The leg increases 19.9 times,
which is very nearly the same as the total increase for the
forearm. The hindfoot increases 17.8 times, or about one
and eight-tenths times the total increase for the forefoot.
The larger percentage increments (not shown) throughout
the entire period for the hind limb and its segments compared
to the fore limb and its homologous segments also evidence
the greater growth of the hind limb and its parts. Further
discussion of the relative lengths will be given later.
The upper curve in figure 4 represents the length in millimeters of the hind limb plotted on body weight in grams, with
386
HOMER B. LATIMER
the males shown as dots and the females as circles. The three
lowest curves represent the linear growth of the three segments of this extremity. As in the preceding figures, the
cases are not shown for these, as the distribution of the individual cases, as seen in the preliminary chart, is very similar
to that for the entire extremity.
Fig. 4 Growth of the hind limb plotted on body weight is shown in the upper
curve with the dots representing the males, and the circles, the females. Individual cases are not given with the curves f o r the segments of the extremity.
Formulae for the four curves are given in the text. The ordinates in the left
margin give the correct value f o r the percentage curve as well as for the other
curves.
The empirical formulae for these four curves, like the formulae for the four curves in figure 2, are all functions of the
cube root of the body weight. The formulae from which the
four curves were drawn are as follows :
Hind limb,
Thigh,
Leg,
Hindfoot,
Y = 16 4 X - 7.00, from 3 to 200 grams of body weight
Y = 5.2 (
Y
T
- 1.00, from 2 to 200 grams of body weight
Y = 3.1 V X + O.O16X, from 3 t o 200 grams of body weight
Y = 7.1 VX--4.00,
from 3 t o 200 grams of body weight
Iii all of the above formulae, Y represents the length in
millimeters of the extremity or its part and X represents the
body weight in grams. I n every case the average percentage
deviation of the calculated from the observed length is less
for the curves plotted on body weight than for those having
PRENATAL GROWTH O F THE CAT
387
body length as abscissae. The leg has the greatest average
percentage deviation in both sets of eight curves (7.07 per
cent for body length and 4.43 per cent for body weight). All
but two of these curves (leg and forearm on body length)
have an average percentage deviation less than 5 per cent.
The lengths of the hind limb reduced to percentages of the
total body length are shoKn in the percentage curve in figure 4. The numbers in the left margin, although marked millimeters, give the correct percentage values for this curve.
This curve rises more rapidly at first than the percentage
curve in figure 3 and it shows no decrease, as is evident at
about 130 mm. of body length in figure 3.
I n general, the growth of the hind limb resembles the
growth of the lower extremity of the human fetus in that all
curves based on body length are straight lilies (Scammon and
Calkins, '29). Lkiewise, the lower extremity of the human
fetus, as we have shown for the hind limb of the cat fetus,
has a smaller initial length and increases more during this
period. Both extremities become increasingly heavier in
proportion to their length, with the greatest increase in the
hind limbs. The weight in grams for each centimeter of
length of the appendage was determined for both extremities
for each 10-gram interval of body weight. The fore limb increased from 0.020 to 1.50 gm. per centimeter of length, or
75 times, between 0.3 and 190.0 gm. of body weight, and the
similar values for the hind limb are, from 0.0216 to 1.98 gm.
per centimeter of length, or an increase of 91.7 times. The
marked differences in the growth of the two extremities are
the greater growth of the hindfoot compared with the forefoot and the shorter leg compared with the forearm.
Scammon ( '30) has shown that the percentage first derivatives for the ponderal growth of both extremities, the hands
and the feet of the human fetus, are remarkably constant for
the latter part of the period. The first differentials of the
eight formulae for linear growth of the extremities and their
parts on body weight, given above, were determined for each
10-gm. increase in body weight. These differentiah were
388
HOMER B. LATIMER
then reduced to peroentages of the length in centimeters of
the extremity, or part, for that body weight, or
(%)IM’.
The
L (ern.)
resulting values for the gain in length per unit of body
weight were also very similar and especially for the later
part of the period. The percentage differentials for the fore
limb and its parts were more constant than the similar percentage differentials for the hind limb and its three segments.
The percentage differentials for the leg length were less than
for any of the other seven dimensions.
RELATIVE GROWTH
The percentages of the lengths of the fore limb and of the
hind limb with reference to the body length have been shown
in figures 1 and 3 plotted on body length and in figures 2 and
4 plotted on body weight. The lengths of the three segments
of each appendage were reduced to percentages of the total
length of the respective appendage, and plotted on body
weight (curves not shown). The percentages of both the
arm and forearm rise rapidly at first. The percentage
lengths of the forearm in all of the cases below 1gm. of body
weight average 27 per cent. This increases to 33 per cent
in the second group of cases and increases but little up to
birth, with a slight decrease in the newborns. The curve for
the percentages of the arm length rises less than that for the
forearm, f o r it averages 36 per cent for all of the cases below
1 gm. of body weight and after a rapid though brief rise it
averages 37.96 per cent from 1to 120 gm. of body weight. It
drops 1per cent in the newborn cats just as the curve for the
forearm does. The percentage length of the forefoot decreases rapidly between the first and second groups, or from
an average of 36 per cent t o 29 per cent in the second group,
and then remains nearly constant.
The three parts of the hind limb are not as constant in
their percentages as are the parts of the fore limb. The
percentages of the hindfoot average 47 per cent for the
first group, or all of the specimens less than 1 gm. in bod>-
PRENATAL GROWTH O F T H E CAT
389
weight. This decreases to 41 per cent in the specimens between 1and 10 gm. in weight and then slowly iiicreases to its
maximum of 43 per cent. The other two segments of the
extremity increase a t first a s did the two proximal segments
of the fore limb, but these vary more than the parts of the
fore limb. The same percentages were plotted on body length
a s abscissae, and the resulting curves were practically the
same as those plotted on body weight.
The most striking thing shown in these percentages is the
relative decrease in the percentage length of the forefeet and
the hindfeet and the corresponding increase in the two proximal parts of both extremities. These changes in the earl?
proportions of the extremities together with the failure of
the formulae to fit the smaller specimens, which has been
mentioned, would suggest that these smaller specimens belong
to the embryonic rather than the fetal period, or a t least that
there is some marked change in the rate of growth between
these smallest specimens and the remainder of the fetuses.
INDICES
The ratios of the adjacent segments of the same extremity
are shown in columns 2 to 5 of table 1. All of the indices
in this table are the averages of the individual indices €or the
specimens grouped according to body weight as shown in the
first column. The number of specimens in the last three body
weight groups is much smaller than in any of the others,
and hence these indices are less significant. The brachial
0 0 )
rapidly at first, and to a lesser
index ( f c r ~ ~ ~ ~ 2increases
extent this is true of the tibio-femoral index ('?$;?).
Both
indices increase slowly and somewhat irregularly throughout
the entire period, thus showing that the proximal segment of
both extremities grows less rapidly than the middle segment.
Scammon and Calkins ('29) report a similar condition for
the human fetus. They find that the distal segments grow
more rapidly than the middle, but this is not true for
the cat fetuses, f o r the third and the fifth columns of
this table show that the forefoot-forearm ( fol;eofroe~lOo) and the
390
HOMER B. LATIMER
hindfoot x 100
foot-leg (--Kc) indices decrease rapidly at first and the
forefoot-forearm index continues to decrease more slowly
throughout the entire period.
All of these indices were plotted and the distribution of
the cases was very good for all of the indices, except the
TABLE 1
Averages of the individual indices, for each 10 gms. of body weight, of the
adjacent segments of the same errtremity and of homologous
segments of the fore limb and the hind limb
BODY
WEIOET,
GRAMS
3RAOHIAL
_ _
74.7
88.9
90.3
88.3
89.4
86.2
88.7
91.8
92.0
90.2
93.5
90.6
$32
96.4
95.4
95.5
95.2
92.7
93.0
95.7
_97.5
_ __
FOREFOOT
FOREARM
~
0.3- 1
1 - 10
10 - 20
20 - 30
30 - 40
40 - 50
50 - 60
60 - 70
70 - 80
80 - 90
90 -100
100 -110
110 -120
120 -130
130 -140
140 -150
150 -160
160 -170
170 -180
180 -190
190 -200
138.8
86.7
82.8
82.5
82.1
86.8
82.1
80.1
78.9
79.9
78.3
78.6
77.7
76.9
80.9
79.3
80.0
80.7
81.5
78.3
77.0
FOOTTIBIOLEQ
REMORAL
_ _ -~
68.3
70.3
69.3
64.4
65.5
62.3
61.9
65.6
67.3
65.9
66.1
63.2
68.0
70.3
74.0
68.4
70.7
74.0
77.0
70.5
70.5
231.1
170.1
161.6
181.7
178.0
186.0
191.4
187.1
186.9
190.6
187.3
192.5
186.9
180.9
171.0
183.8
177.5
173.1
173.0
181.0
181.0
INTERMEMBRAL
_
_ ~
131.7
117.1
107.8
106.6
105.2
103.2
103.6
102.5
100.1
101.3
102.4
101.6
99.8
97.7
94.9
95.0
96.3
94.3
94.5
96.3
98.5
HUMEROFEMORAL
HANDFOOT
137.2
127.2
114.2
113.6
112.6
109.5
110.7
110.4
110.3
110.4
111.1
110.3
110.0
106.8
104.3
103.0
105.0
106.0
109.0
105.7
107.0
94.9
82.8
77.3
73.2
71.5
71.3
68.8
66.9
64.5
64.9
66.2
64.7
63.5
63.2
63.7
62.3
63.5
62.0
62.0
62.3
63.0
~~
foot-leg index. The curves are omitted t o save space.
The
values for this last index are probably of less significance
than the others, due to the very wide variation in the indices
for each group.
The last three columns of this table give the average
indices f o r the homologous segments of the fore limb
and the hind limb. The general trend of the intermembral
index (fozi+:%:g)
is similar to that of the human fetus and
PRENATAL GROWTH O F T E E CAT
391
the indices are shown in column 6, table 1. The average index
f o r the smallest fetuses is 131.7, and Schultz ('26) gives a
percentage of 132.7 for the human fetus at 9 weeks. He finds
that the upper extremity is longer than the lower, except at
34 weeks of age. The fore limb of the cat is shorter for all
body weights above 113 gm. The index of 94.2 per cent given
by Scammon and Calkins ('29) for the newborn human is
similar to that found for the newborn cat. Their values at
first are lower than those given by Schultz or the indices for
the cat fetus.
The ponderal index ( y . ~ ~ ~ h ~) ~was
b ~ computed
~ - "
from
table 3 of the first paper of this series and, unlike the intermembral index, it increases from 125 at 0.3 gm. of body weight
to its maximum of 170.2 at a body weight of 1 gm. and then
it decreases to 74.4 in the largest specimens.
Next to the last column in table 1 gives the humero-femoral index ( ~ ~ K and
, ~ it~ shows
~ ) that the arm is longer than
the thigh throughout the entire period. The last column girforefoot x 1 0 0
ing the hand-foot index (mT) shows that the forefoot
is shorter than the hindfoot in all of the specimens except a
very few of the smallest, and these are probably too small to
be counted in the fetal period.
Another index frequently used is the ratio of the length
of the extremity to the trunk length. The trunk length was
not measured in these fetuses, but as a substitute for this the
difference between the nose-anus length and the head length
(given in the previous paper) or the spine length was used.
The computed length of the fore limbs x 100 divided by this
spine length was determined for each 10-mm. increase in body
length. The value of this index increases from 25.8 in the
smallest specimens to 53.7 at 200 mm. of body length. The
similar indices for the hind limb and for the same body lengths
are, 17.2 and 53.0. The increase in both indices is most rapid
at first, with the greatest total increase in the hind limb-trunk
index.
392
HOMER B. LATIMER
SYMMETRY
The asymmetry of the adult human appendages has been
recognized for a long time. Recognition of this condition in
the fetus is of more recent date. Bartelmee and Evaiis (’26),
Schultz ( ’26 and ’30)’ and Schaeffer ( ’28) give ample discussion of the problem and good bibliographies. Table 2 gives
the frequency and the percentage frequency of the occiirrence
of equal lengths or of longer right or longer left measurement.
There seems to be no ‘crossed symmetry,’ as suggested by
Schaeffer (’as),for the total length of the appendages, for
TABLE 2
Asymmetry of the eight dimenstons of the two extremities
LEFT LONGER
RIGHT LONGER
- -- - _ _
MBASUREMENT
Number
1
Per
Number
of eases
114
79
102
lli
114
106
121
83
of eases 1
cent
.~
-~
__- - _
114
I --45.42
Fore limb
- __
Arm
Forearm,
Forefoot,
Hind limb
Thigh
Leg
120
105
88
112
101
95
113
1
I
1
j
1
47.80
45.63
34.92
44.62
41.74
39.26
46.69
-
S A M E LENGTH
Per
cent
Number
of eases
Per
cent
45.82
31.48
40.08
45.24
45.42
43.80
50.00
34.30
22
52
36
50
25
35
26
46
8.76
20.72
14.29
19.84
9.96
14.46
10.74
19.01
both limbs are longer on the left side, but not significantly
so. We do find a ‘crossed symmetry’ as far as the segments
of the extremities are concerned. The arm and the forearm
are longer more frequently on the right side and the thigh
and the leg on the left side. The left forefoot is more frequently longer (56.4 per cent of all asymmetrical cases) and
the right hindfoot is longer in 57.7 per cent of the asymmetrical cases. Thus the rather marked asymmetry of the
distal segment of each extremity almost seems to balance
the asymmetry of the two proximal segments with a resulting
very slight asymmetry of the total length of the appendages.
PRENATAL GROWTH O F THE CAT
393
SUMMARY
The linear growth of the fore limb and its three parts and
of the hind limb and its three parts, plotted on body length,
form straight-line curves. The empirical formulae for the
same eight curves plotted on body weight are all functions
of the cube root of the body weight.
The sixteen formulae fit the cases fairly well, for the average deviation of the observed and the calculated values are all
less than 5 per cent, except for the forearm and the leg
plotted on body length. The curves plotted 011 body weight fit
the cases better than those plotted on body length.
The lengths of the hind limb, leg, and hindfoot show a
marked increase in the newborn cats over the lengths in the
oldest fetuses. The other dimensions continue as smooth
curves into the newborn stage.
The fore limb increases from about 20 to about 40 per cent
and the hind limb increases from about 10 to a little over 40
per cent of the body length.
The hind limb and its segments increase more in length
than the fore limb and the homologous parts of the fore limb.
The hind limbs become heavier per unit of length, and to a
somewhat lesser degree this is true of the fore limbs.
After a body weight of 10 gm. is attained, the relative
lengths of the segments of each extremity change but slightly
with reference to the length of the entire extremity. I n the
smaller specimens the percentages of both forefeet and hindfeet drop rather rapidly, while the lengths of the other parts
increase, with the exception of the leg, which does not change
as much as the others.
The indices of the adjacent segments of the same extremity
show that the middle segment of each extremity, in general,
grows more rapidly during the fetal period than the most
proximal segment. The forefoot-forearm index decreases
during the fetal period.
The intermembral, the humero-femoral, and the hand-foot
indices all decrease, rapidly at first, and then more slowly
until the newborn stage.
394
HOMER B . LATIMER
The two extremities do not show a significant asymmetry,
but all of the segments of the extremities show a ‘crossed
symmetry. ’
L I T E R A T U R E CITED
AKIBA, TAKASHI1924 Uber die Korperproportionen der japanisehen Feten.
Folia Anat. Japonica, Bd. 2, S. 189-219.
LATIMER,
H. B., AND JOHN
M. AIKMAN 1931 The prenatal growth of the eat.
I. The growth in weight of the head, trunk, fore limbs, and hind
limbs. Anat. Ree., vol. 48, pp. 1-26.
LATIMER,
H. B. 1931 The prenatal growth of the eat. 11. The growth of the
dimensions of the head and trunk. Anat. Rec., vol. 50, pp. 311-332.
REIGHARD,
JACOB,
AND H. S. JENNINGS
1901 Anatomy of the eat. Ncw York.
S r A M N o N , RICHARDE. 1925 Section on developmental anatomy. Morris ’ Textbook of Anatomy, edited by C. M. Jackson.
1930 The ponderal growth of the extremities of the human fetus.
Am. J. Phys. Anthrop., vol. 15, pp. 111-121.
SCAivhiON, R. E., AND L. A. CALKINS 1929 The development and growth of the
external diniensions of the human body in the fetal period. The
University of Minnesota Press.
SCHAEFFER,
A. A. 1928 Spiral movement i n man. J. Morph. and Physiol.,
v01. 4c7, pp. 293-398.
SCHULTZ,
ADOLPH H. 1926 Fetal growth of man and other primates. Quart.
Rcv. Biol., vol. 1, pp. 465- 521.
1930 The skeleton of the trunk and limbs of higher primates.
Human Biol., vol. 2, pp. 303-438.
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