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The relative postanatal growth of the systems and organs of the chicken.

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THE RELATIVE POSTNATAL GROWTH O F THE
SYSTEMS AND ORGANS O F THE CHICKEN1
HOMER B. LATIMER
Department of Zoology and Anatomy, University of Nebraska
TEN CHARTS
The growth of the body, systems and organs of fhe singlecomb White Leghorn chicken has been described in a recent
paper, but a comparison of the growth of the various parts
with reference to the entire body growth was not given, and
so this little study has been undertaken to show the relative
changes in the growth of the systems and organs between
hatching and maturity.
MATERIAL AND METHODS
The data on which this study is based are taken from a
previous paper (Latimer, '24) in which is reported the
growth of 100 single-comb White Leghorn chickens, raised
at the University of Minnesota and ranging in age from
day of hatching to 300 days of age, with three specimens
about one year old and three about two years old. The details
of the study of the growth in gross body weight and of the
methods of making the autopsies are given in the earlier
report and will not be included here. All of the weights in
grams given in this paper were determined by using the
empirical formulae given in the earlier report and the percentage values were secured by inspection of the percentage
curves used in the preparation of the charts of the earlier
paper. The percentage weight in all cases is the weight of
Studies from the Zoological and Anatomical Laboratories of the University
of Nebraska, no. 141.
233
THE ANATOMICAL RECORD, TOL. 31, NO. 3
234
HOMER R. IJATIMER
the system 01-organ reduced to a percentage of the net hody
weight, or the weight of the chicken immediately after killing
millus tlie weight of the contents of the digestive tulx. The
method of tletermining the ratios of the percentage weights
is the same as that used by Doilaltlson ('23) in his study of
the albino rat. I wish to express my thanks to the Departm c i i i t of Anntomy of the University of Jlirinesota f o r making
possihle this series of studies 011 the gron-th of the chicken.
TOTAL INCREASE I S \VFXGHT
'rlie total inorease in weight from hatching to maturity is
not t l w samc for the various systems and organs of the
cliickcii, but ranges from an increase of about sevenfold for
the ctliitral iiervous sytclm t o a maximum of 214 times f o r tlie
pancreas. The growth iiicrcases for the various parts are
summlirizetl in table 1 .
The first columii of' table 1gives the name of the organ o r
system ; the secoiicl coIumIi, the hatching weight in grams,
; i l i t l tliv third column gives the weight at maturity. The last
column gives the ratios of the weight at maturity to the
1i;itcliiiig weight. 'L'Eiese ratios greatly facilitate comparisoii
of tlie growth in weight of the various parts. A study of
tliis taltle will show that the integument and the gross body
wt4glit each increase a little over 'TO times, a i d that there arc
tweiitj- parts iiicreasirig less than 70 times and hut three
wliicli increase more than the gross body weight. As is to be
expected, those parts and organs which have a precocious
development increase less in postnatal life. The central nervous system and the eyeballs increase but 6.6 times from
hatcliing to maturity, followed by the hypophysis and thc
bead of the females. A study of the postnatal growth of tlie
ceiitral riervous system of the domestic fowl (Latimer, '25)
shows that the braiii aiicl the spinal cord do not increase an
equal amouiit between hatching aiid maturity, for the cord
iiicreases 19 times during this period and the brain iiicreases
but fourfold. There is a dieerelice in the total increase in
tlw parts of the h a i n , although iiot so great a difference as
that bch-eeii the brain arid the cord.
233
I'OSTNATAL GROWTH OF C H I C K R S
The head of the male chickens increases over twicc as much
as does the head of the females, but this is due largely to the
heavy comb and wattles of the male fowls, the comb, wattles,
and ear lobes being included in the weight of the head of
both sexes.
TABLE 1
libcrease in weight of the various oiyare and ajaienu,
.---
.........
..
.
--
...............
. ~.
-.
Nervous s m m ............
Eyeballs.
Hypophgeia ...............
Head (female) .............
8tOmacli ...................
Digeative tube ............. i!
Gizzard.....................
Int&n&q
i
j
Head (male)
Viscera. ................... i
Suprsronala
/
Liver ......................
I
Kidneye.
Skeleton (female) ...........
Skeleton(male) ............ 1
Heart .....................
j
Spleen ....................
..................
'
.................
..............
...............
...................
1
Grow body weight.. .......
................
!
Thyroid ................... :
Muscnlature ...............
Pancreas ..................
Thymus ....................
Feathers (female). .........
Feathem (male) ...........
integument
.
....
!
-.
- -- I
I
HATCHING
PRIUliT IN
BNAMS
.-
1.00
0.80
0.0021
4.0
0.40
4.67
1
j
2.0
1.87
. 1
4.0
6.89
1
0.W
1.6
0.4
6.2
5.2
0.D
0.04
37.0
8.1
8.2
om26
0.02
1
I
.
.
1
1
!
j
1
53.2
5.78
107.8
60.2
Fio.6
112.8
1W.7
0.2454
60.9
15.3
201.2
254.1
13.7
2.58
2800.0
217.1
0.284
1257.3
4.B
1
!
;
i
.
1
:
1
13.3
14.5
23.0
26.1
25.0
28.2
28.3
31.8
33.9
j
38.2
38.5
,
48.9
'
I! :
70.0.3
m.3
113.6
214.0
8
0.10
1.8
1.8
i.5
0.76
I
i
64.9
M.Ci
61.3
81.6
....
The viscera increase a little over 28 times, or but a little
more than the head of the male. The weights of the viscera
as given in this table are the sums of the weights of the
various organs, a list of which is given in table 2, which gives
the ratios of the percentage weights. The lungs are not
iiic~lutlctl, unfortunately, for after 1200 grams of gross body
weight lhev were so variable that 110 formula was deduced and
1 1 0 CIII'VC' drawn. The weights of the two lungs and the tra(hea togctlier for each chicken are shown plotted on the chart
in figiire 19 of the previous report.
The male skeleton iiicreases more than the female skeleton,
or 49 times for the male and but 39 times f o r the female
skeleton. The male skeleton is followed by tlie heart, which
increases 55 times and tlic spleen which increases 68 times,
or nearly as much as the total body weight increase.
The th;vroitl, the musculatnre, and the pancreas each increase more than the total body weight increase, the values
are respectively, 114, 153, and 214 times. The thyroid and
the pancreas each form but a relatively small part of the total
body weight, but the skeletal muscles increase from 22 per
cent of the net body weight at time of hatching to 48 per cent
in the adult fowl. An increase of over 150 times in the absolute weight of a part forming so large a percentage of the
entimi body weight would naturally account for the larger
Iiiirn1)c.r of organs iiicreasing loss than 70 timcts, or the in(wvise for the entire body from hatching t o maturity. 1'11~
larg:.eillcl*eiis(?in the thyroid weight is clue in part, a t least, to
t l i ~iiic.iused amount of colloid and the increase of 314 times
f o r thcl paiicwas may bc due to some extent to the difficult?in i.t~moving2111 of the glaiid in the newly liatched chicks.
?'lit> iiicreasc, of the thymus aiid tlie feathers f o r tlie male
; i i d tlic female are listed as tlie last three organs in table 1,
for although they increase, respectively, but 8, 48, and 65
times their hatching weights ut maturity, they do hare maxima much higlier than these figures earlier in their growth.
Xt its maximurn the thymus is 61 times its hatching weight,
or a little over 8 times tlie ratio at maturity. The feathers
of the fernale a t their maximum arc 1.3 times the ratio a t
maturity and the maximum for the male plumage is a little
over 1.2 times the ratio at maturity.
237
POSTNATAL GROWTH OF CHICICES
RELATIVE PERCENTAGE WEIGHTS
The weights of the various organs and systems reduced to
percentages of the net body weight are shown plotted against
the gross body weight in the previous paper.
The individual percentages were plotted on a preliminary
chart and a mrve was drawn by inspection through the
-.
..
.. .
..
GKOSS BODY
w E w m IN .
GKAMS
I.IVF.I~
I .Oi
300
500
700
1100
1300
1500
1700
1900
2100
2300
2~
.
. . . . . .. ..
KIDBEYS
TIIYXUS
,
100
1300
..
.
i
I
I
O.!U
0.88
0.84
0.80
0.76
0.71
0.67
0.61
0.57
0.53
i
+WIG
,
~
1
:
I
,
j
1
1.00
1.83
1.w
1.81
1 . ti0
I .46
1.31
1.15
1.oti
0.99
0.91
0.88
0.80
0.73
~
I
1 .00
0.97
0.84
0.75
0 . ti:)
0 . ti0
0.5i
0.58
j
0.m
0.65
0.66
0.66
0.66
I
!
1. 00
2.50
4.17
3.83
3.34
3.50
3.67
3.17
2.67
2.42
2.17
2.08
2.00
1.83
I
i
i
~
I
~
I
1.00
0.!)2
0.72
0.7ti
0.89
I
0.98
1.01
1.02
1.03 I
1.04
1.07 '
1.15
***
* **
~
'
I .oo
1.72
1.50
1 .25
1.@2
0.92
o.,o
0.69
0.64
0.58
0.56
0.56
I
II
I
i
I
I
1.oo
1.05
1.27
1.47
I .tie
1.71
1. i 8
1.45
1.00
0.64
0.44
0.31
0.20
0.09
cloii~,lc-~~-c!ightctl
mcdiaiis, o r the averages for hoth tlie p t ~
cwitage weight of the organ aiitl tlie gross 1)ocly weight for
c.ac.11200 grams' iiicrease i i i body wiglit, aiid this curve witlioiit tliti iiidivitluul cases is showii a s the lighter line in the
cliarts iii the previous paper. Thc percentage values read
from tticse ~ i i r v e sw c i ~ilsetl in conipntirig the ratios f o r this
iq)ort. 111 many cases tllc origiiial data \\-ere coiisulted in
\. P 1-if i c i i t i ()II ( )f t 1I
p ~ reii
c t a gc s . 'l'li c 1)erc en t a ge we igI i t ;it
Iiatcliiiig was takeii a s unity aiid the ratios of the percent;igw f o r each orgm a t 100 gr*arns aiicl for each 100 grams'
iiicreaw i i i gross hody weight thereafter were tletermiiied.
P'ig11rw 1 to 10 show t l ~ c wratios grapliically a11d tables 2
ant1 3 give tlic ratios for hatching, 100 grams and each 200
mxms ' iiicrensc iii g'i'oss body weight tlicreaftei-. 'I'liis
t iwitmciit makes a cwmparisoir of tlic cliangcs iii tlie perwiitagw \ w - y much easier than N dircct iiispection of tlic
i~wcciittigecurves.
'I'lit~ ratios for tlic viscera a i d the individual orgaiis whieli
arv listed as viscera are given iii table 2. The sum of tlic
~)(weiitages
of the inclividual organs given in this table werc
iitltlt'(1, aiicl tlicse results were treated as were tlic pcrcwitagcs
of tlie individual organs, aiid these ratios are given in the
w ~ o i i ~cwlumii,
l
the gross hotly weights being given iii tlie
timt columii. The ratios f o r the digestive tube, gireii iii tlie
fifth eolumii, are the ratios for the sums of the parts of the
cligestive tuhe, namely-, tlie stomach or Iwoveiitriculus, tlie
giaxard mid the intestiiies, esopliagus, imtl the c w p d l
weiglicd together. These parts are gilreii separately as well
iis tlicir sum, mid 2111 the ratios ai'c for. tlie empty tligestil--e
tube 01'its parts. To complete tlie list, the luiigs a i d trac1ic.a
4 1 o i i l ~ lbc inrlu~led,h i t , as previons1)- stai ecl, they were S O
varialde in weight that it did iiot seem wise to iiiclude them.
r!'11(31~~~ were 1 1 0 apparciit pathological luiigs in the group-at least, 110 pathological specimens w r e noticed in making
tlitl autopsies.
' h e ten viscera (male and female together) listed in table 2
forin 21.4 pcar writ of tho net hotly weight at time of hatching.
ch
239
POSTXATAL GROWTH OF CHICICES
This rises to 21.7 per cent at 100 grams oP body weight aiid
then slowly decreases to 8.3 per cent in the adult. These
ralues of course do not include the percentage weight of the
lungs and the submaxillary which are included by Donaldson
('23) in tlie percentage weights of tlie viscera of the albino
rat. The viscera of the male albino rat form 10.9 per cent
of the body weight at birth, 19.2 per cent at 25 grams of body
weight, and then decrease to 10.5 per cent in the adult. These
figures shou~that at birth tlie percentage weights of the visTABLE a
f?c.lativua perccntage weigkta of the puvtr and syrtems
- .
..
I
_
...
........
. . .
FEATHI<Krl
(SALE)
.
1 .OO
0.63
0.33
0-26
IKW)
1100
1300
1500
1700
1 0
21100
m
''ti00
0.20
j 0.17
0.15
0.14
0.12
0.11
0.11
I
0.097
' 0.090
0.081
'
1
.......
1.oo
0.68
0.41
0.33
0.29
0.25
1.00
0.66
0.41
0.41
0.37
0.23
0.21
0.31
0.29
0.21
0.30
0.19
0.31
0.33
0.18 0.33
0.18
0.18
0.18
'
.
0.34
0.37
.
..
-
1.OO
1.07
1.07
1.8
1.06
0.76
0.68
0.83
0.60
0.68
1.01
0.96
0.89
0.82
0.76
0.74
0.69
0.40
0.68
0.65
- ..
. .
.
-
.........
1.oo
1.07
1.Oi
1.09
1.05
1.w2
0.89
1.QL
1.02
:
I
._. . . . . .
1 .oo
.......
1.41
1.75
1.87
1.96
2-00
2.04
1.oo
1.41
2.00
2.16
2.24
2.40
2.66
1.00
1.41
2 .00
2.16
2.24
3.40
2.65
2.07
2.54
2.10
2.12
2.14
2.16
2.17
2.00
1.69
1.38
1.10
2.59
2.64
2.40
2.16
1.84
I .67
2.19
. . . . . .- _.
. . . . . .
. . . . . .
(exc-clding the lungs) are just a little
less than twice as great as those of the viscera in the rat.
The maximum percentage weights are more nearly alike, for
the chicken viscera are now hut slightly heavier than the
viscera of the rat. At maturity the viscera of the rat form
a larger percentage of the body weight than d o the viscera
of the chicken.
Similar data are given in table 3 for the systems and parts
of the body iiot listed as viscera. The central iiervous system
is given all togctl~erhere, as a study of the growth of the
1
240
HOMER B. LATIMER
parts of the brain and of the spinal cord of the chicken has
been published (Latimer, '25).
As stated above, the values used in determining the ratios
given in tables 2 and 3 and plotted in figures 1to 10 are taken
from the curves drawn by inspection. There are, of course,
individual variations in the percentage weights and these are
referred to in the earlier paper, the curve merely giving the
Fig. 1 The percentage weights of the eyeballs (upper curve) and the hypophysis (lower curve) reduced to ratios of the percentage weights at hatching plotted
against gross body weight in grams.
median values for each body weight. A careful study of the
distribution of the cases for the digestive tube shows that
the percentage growth of this part increases for the first six
days and that there is also a similar very brief rise in the
percentage values of the liver (fig. 5 ) . The curve for the
entire digestive tube is not shown. It follows the curve for
the gizzard (fig. 4) very closely, and so it was not drawn on
the chart. The data are given in table 3.
It will readily be seen by a study of the curves in figures
1 to 10 that thcre arc four types of curves. There are, first
of all and found in the largest number of cases, the curves
which decline from hatching to maturity. Included in this
type are the central nervous system (brain and spinal cord),
eyeballs, hypophysis, glandular stomach o r proventrieulus,
entire digestive tract, gizzard, head (both male and female),
Fig. 2 The percentage weights of the suprarenals (upper curve) and the
entire central nervous system (lower curve) rrduced t o ratios of the percentage
weight at liatching plotted against gross bod? weight in grams.
suprarenals, and the heart. While the heart is listed in this
group, it does show a rise toward the latter part of the period,
f o r after a minimum ratio of 0.57 at a gross body weight of
1300 grams the ratio slowly rises to 0.6G at 2100 grams and
remains at this level up to maturity.
I n the second group of curves are those which rise to a
maximum after hatching and then later decrease t o a ratio
less than unity, or to a smaller percentage of the net body
weight than at hatching. This group includes the following :
I ) R I I ~ I ’ C R S , liver, iiitcstiiics (including esophagus a i d crop),
i4scchr.n (sum of organs listed in table a ) , lcidncys, ligamenl011s skelctoii (hot11 male and female), and tlie tliymns.
111 the thii-d group a3.e listed tlic two orgaiis which rise t o
i\ maximum after liatcliiiig and theii clecroase slightly, hut
whosv ratio I-emains greater tliaii niiity, or wliicli form R
larger. pt!rcmtage of tlie net body weight even at matuvit?
tlitlii they (10 at time of Iiatcliing. The feathers a i d the spleen
t\vo ciii*vos iiiclutled iii this group. E’igurc 10 slio\vs
t l i a t t h e fcmt.ilc plumage w t i i i m to I ~ C R I ’tlic
~ ~ same p e i ~ c i i t age of the net body weight at maturity as it formed a t liatcliing. The mrw showing the ratios of the percentage weights
ot’ t ~ i esplccn (fig. 8 ) shows-two maxima, the first wliicli is
also the most marked at 300 gi-ama of gross body ~veiglit
t i i d tlic second a t 1000 or 1100 grams of gross body weight.
The fourth group, or those p a r t s with a ratio greater than
imity or a larger perceiitage of thc net body weight at
rn:it~ii*itytlim at time of Iiatching, iiicludes tlic thyroid and
>ii*ih
tlich
243
POSTNATAL GROWTTI OF ('HICYEN
tlie muscnlature. Tlie thyroid (fig. '7) drops to a minimum
ratio of 0.72 at 300 grams of gross body weight, but rises
thereafter., attaining a maximum ratio of 1.15 at 2100 grams
of gross body weight. After this body weight the thyroid
was so variable that. it seemed best to carry the curve to this
point only.
PER.IODS O F MAXIMIJM PRBCESTAGE WEIGHTS
Table 4 g i w s the gross body weights at which the maximum
percentage ratios occur for the various organs. There are
TABLE 4
H o t l ! ~ moiglit.s at zclaich tlie organs
nrirl
systeiibs
attain their maxintum
percentage weight
.....
.. .. . .
..
.. ...
I
. .. .
..
'
-
on(iAxs
-.
Kcrvous systeiii
'
Hypophysis
E yehalk
Tlatching or 37 grmis Head (male and feiiiale)
ITeart
Suprarenal~
Gizzard
StomRrll
'
Digestive tnlie
'
"'
Skeleton
I
I
Thyroid
J l ( K ) grarriM
?(%XIgrams
Thymus
Feathers
I
?olusculatare
Pancreas
Liver
Iritestiiiex
Viscera
100 grmw
.. .
Kidneys
Spleen
300 grams
...
iiiiie organs and s p t e m s of the chicken wliich have this maximum percentage at time of hatching. The braiii arid the
spinal cord are here takcii together, but each, as previously
shown, has its maximum percentage of the net body weight
at time of hatching. This initial maximum is found in the
case of the eyeballs, the hppophysis, the head, the heart, and
the entire digestive tube. The maximum f o r the digestive
tube, as described above, really comes on the sixth day. A
comparison of this tahle with table 1 given by Donaldsoii
('23) shows that of these nine entries in table 4, but one,
the li~-pophysis,forms its maximum pereelitage at birth in the
alhino rat. Donaldson gives the luiigs, the Iiypophysis, and the
tliyroitl as forming their maximum percentage weight a t birth
in the rat. IiIxamination of the percentages of the chick
luiigs sliows that they, too, might be included in this list, for
\vitliont tloulif their maximum percentage weight occurs at
F'ig. 1 The ratios of
gizzard (middle curve),
weight in grams. The
folloas very elost4y the
the l'arts of the digestive traet, intestine (upper curve),
and stomach (lowest currej, plotted against gross body
curve for the entire cmpty digestive tract (not shown)
curw for the gizzard.
t i r w of hatcliiiig. Tliis would make two orgaris witli 8 commoil maximurn percentage weight a t birth in the chick and iii
tlie alhirio rat, namely, the lungs and the hppophysis. The
pcrcwitage of the thyroid does decrease for a time in the
c*liick (fig.7 ) , but it later. increases t o a greater relative weight
a t 2100 grams. The maximum relative weight of the lieart
of the chick at hatching may be explained by its grcater activit!- compared with that of the ncw.horn rat, thus necessitat-
POSTXATAL GLtOTVTH OP C€€ICI<EN
245
ing a much more effective circulation in the chick. Joseph
('08) has suggested that the activity of an animal is directly
correlated with its heart size. The precocious development
of the digestive tube in the chick may be explained by the
differciice in the diet--.the rat is nourished by the maternal
Fig. 5 The ratios of the pancreas (upper curve) and the liver below plotted
against gross body weight in grams.
milk, while the chick must eat nearly the same diet as the
adult, and hence it needs a digestive system fully able to care
for this complex food. Donaldson ('23) finds the maximum
percentage weight of the digestive tract of the rat at a body
weight of 31.1 grams, or a t about six times the birth weight.
Jackson ('13) finds the head of the albino rat reaching its
maximum relative weight at seven days, but in the chick this
maximum occurs a t liatching. This may be cxplairiotl by
tlie better development of the eyes and central nervous sysiii the chick, agaiii illustrating the better development of
the chick at time of hatching compared with the albino rat,
tchm
Fig. 6 The ratios of tlir percentage weights of the musculature and tlw
kitlnrys plotted against gross body weight in gr:irns. The curve whic.11 rises
cwiitiiiuouuly is that of the musenlnture.
whicah is born blind arid dependent upon maternal protectioii
arid food supply, while the chick, if supplied with a sourcc
of artificial heat for part of tlie time, will get along fairly
well. The suprarenals of the rat reach their maximum pcrwntage weight when the body is about five times its birth
weight, hut in the chick they are relatively largest at hatching.
POSTNATAL GROWTH O F CHICKEK
247
The pancreas, liver, intestines (including esophagus and
crop), and the sum of all the viscera attain their maximum
at 100 grams of gross body weight.
The spleen and the kidneys do not attain their maximum
percentage until a body weight of 300 grams is reached, or
at about forty days of age. This retardation in the attainment of the maximum percentage weight of the kidneys may
be due possihly to t h o emhryonic elimination of the nitrogenous waste through the allantois and the fact that the kidneys
do not function very extensively until after hatching. Figure
Pig. 7 The ratios of the thyroid and the heart plotted against gross hody
weight in grams.
8, which shows the graphic representation of the ratios for
the spleen, shows two maxima, one which is the greater, at
300 grams and another a t 1000 or 1100 grams of gross body
weight.
The skeleton reaches its maximum percentage weight at
500 grams, o r between sixty and seventy days of age or
slightly after the end of the period of most rapid percentage
increase of the skeletal musculature. Jackson and Lou-rey
('12) report a slight increase in the percentage weight of
the skeleton of the albino rat during the first week of postnatal life, and then, following this maximum, the percentage
neiglits tlecrc~asc to maturity. ‘I’hc musculature does not
reach its maximmim iiiitil maturity, I)nt its period of most
ral)i(l i*cllati\rc growth is passed hy the time the 1)ody has
attwiiitd ;I weiglit of about 300 grams. It is iiiteresting to
iiotti that the maximum percentage wciglit of tlie cerebellum
( L a t h e r , 9 5 ) also occurs at from 400 t o 600 grams of gross
hotly iveiglit, suggesting the similarity in relative tlcrelopmcwt of the skeleton, musculature, and the cwebellnm.
b’ig. 8 The mtios of tlie perceritngr wciglits of the spleen plotted :(gainst
gross lrody weight iii gmiiix. The scale of tlic oidiiintes liere is onc’ Irnlf that o f
l l i r otlicr fig1irc.s.
1 lie thymus aiicl the feathers present similar ratio c u r w s ,
t ~ c c p tthat there is a sex tlifreiwice in tlic Iwrceiitagcs of
t h e feathers and iioric in the Case of tlie t h j ~ n n s . Rotli reach
tlitair rnaximum relatirc weight at 1100 grams, o r at the same
time as the sccoiicl maximum for the spleen. Riddle
in a iwwit pnblication, has describetl a growth curve of the
thymus in pigeons similar to tliat of the chiclien.
The relative weights of the thyroid are showii in figure 7
from hatchiiig to 2100 grams of gross body weight only, f o r
r 1
(’as),
after this time the weights of the iiitlividiial thyroids varied
to sucli an extent that it seemcvl hest to exclude these weights
POSTNATA4L GRO\T'TH
O F CHICKEN
249
as unreliable. Some of tlie heavier adult thyroicls map have
been pathological, and so, while the individual weights arc
indicated in figure 2 1 of the earlier paper, tlie formula aiid
the data are carried to 2100 grams of gross body weight only.
The musculature increases up to maturity. Some of this
increase in the older chickens may be due to an iiicreased
amount of fat stored within the muscle and which could not
Fig. 9 The ratios of the skeleton (ilbove) and the head (Lclow) plotted
:igainst gross body weight in grams. Both curves show ii sex differeiice in the
1:jtter purt, the UTJPW p r t of cwch repwscwts tlic iatios f o i t h e nialt~sa n d tho
lower, the females.
he separated mechanically from t h e muscle tissue. .Jtwkson
and Lowrey ( '12) find the musculature of the newborn albino
rat forming 24.4 per cent of the net h d y weight. Tn the
one-week-old rat thev find this percentage reduced to 22.8
per cent, and following this an increase to 45.4 per cent in
the adult. The chicken musculature iiicrcases continuously
from 22 per cent a t time of hatching to 18 per cent a t
maturity.
T I i L I N A T O Y I C ~ LRECORD, Yola. :II, YO. '!
250
HOMER B. 1.ATIMER
TIIF: LIFE CYCLE IK THE CIIICKEK' A N D I S M A S
1)oiialdsoii ( '18) has sliowii that from hirth to old age mail
tievelops one-thirtieth as fast as tlie albino rat, but the
gi-owth of the chicken docs not show a constant ratio to the
grou-th of' mail. The comparisoii of the growth of tlie chicken
arid of mail for six periods is shown in table 5. During the
fimt two pc'riods, or tlie embryonic period and the time iii
~ ~ i i i ctlie
l i loirtli weight is doubled, the chicken is growing 1 3
times faster than mail. After this tlic growth is accelerated
in tlic chick, as cwmparetl with the liuman growth, f o r the
chick triples its hatching weight in twentythree days aiid
miiii in oiie year, or oil(\-sixtceiilli tliri time required by man.
TABLE 5
(:,nwth of the chicken conipaietl uitk t h a t of man
I
'
1~1~1<1011~
CHICKEN
........
b h i I I r yo11ic
'
\TAN
RATIO
.'I
...............................
I ) c d ) l t ~birth weight. .....................
Tlime t.imes birth .weight...................
Pnl1crtg ( fe1ll:llr) . . . . . . . . . . . . . . . . . . . . . . . . .
cirowth in length CC'~LRCS...................
l..)ltl>lgc..................................
This acceleration is further iiicreased in the comparisoii of
thc times of pnberty f o r tlric female of both species and for
tlic time of tlie cessatioii of iiicrtmc in body length. 111 both
of these tlie ratio is one-thirtieth, or these two periods are
rcwalictl by t l i c c,liic*Bin ono-thirtieth the time required by man.
T l i c b time of pu1)crt.y is given as six months for the females
oiily, as this period can be more easily determineci in the
female fowl. !J'his age may be a little too early, a i d yet in
both tlie chick and in man there is a wide variation in the
ago of pulwrty, a l i d so hoth are merely approximations.
Sclincidcr ailti Duiin ( '24), in their study of the lengths of
the boiicls of Ihe fowl, conclude that the bone length is comp l d c d by eight rnoiitlis of age in the Tleghorii. The slreletoiis
of the prcsent series of cliickcns ase being studied (Latimer,
POSTNATAL GROWTH 014’ CHIC’I.il3N
251
’23) and the ossifications of the long bones are all completed
before the two hundredth day, so the cessation of growth in
length is placed at eight months f o r the chick.
The last period, or the age of the chicken comparable to
ninety years in man, is more difficult to determine, for
Fig. 10 The ratios of the feathers (above) and the thymus (lower eurvcj
plotted against gross body weight in grams. The curve for the feathers shows
a sex diffrrenee after 1100 grams, the upper arm of the curve rcprcsrnting the
ratios for the males and the lower, the females.
chickcns usually do not die of old age, and so this is more o r
less an approximation. Seven years may be too young. I
have learned of two bantam hens which lived to be ten and
twelve years old, and the one which was accidentally killed
at ten years layed up to nine years of age. The men in our
Poultry Hnsbandry Department feel that seveii years is R
fnii. cstimate, altliougli there seem to be 1 1 0 tlefiiiite data 0 7 1
this point. 3 1 1 age greater than seven years for tlie chicken
tvoiil(1only accentuate the point of the chart, namely, that thc
time of old age i u tlie chicken comes back to the same ratio
i t s the first two periods or possibly less tlla~lthis ratio.
\Ire may coiic~ludcthat the cliickeri matures more rapidly,
thus leaving a relatively longer period of maturity than is
fonncl in man. The cliiclteii urliicli belongs to ti lower order of
vertebrates thus has a shorter period of growth a i d a relativcly longer period. of mature life when c,ompai*etlwith tlic
glY)\Ytll cycle of mall.
SIJ M1\1A K 1-
1. The gross body m-eight of the cbickeii increases 70 times
fiwm liat~hiiigto maturity. The central nervous system, e:-cl)w11s, a i d liypopliyais iiicrease but about 7 times, all tho
viscera together increase 28 times, and but three structures,
t h o thyi*oicl,the musculature, a i d the pancreas, increase m o i ~
tlian 70 times.
2. ‘Plie percentage weiglits of the systems aiitl organs ITtliiced to ratios of tlie percentage weiglit a t time of liatcliiiig
fall into fonr groups : a ) those parts TTThiCh decrease from
liatcliiiig to less than the hatching percentage a t maturitythis group includes the larger numher of systems and organs ;
1)) those parts wliicli rise to a maximum after Iiatcliiiig, Init
a t matnritp hare a smaller percentage than a t time of hatching;
the third group iiicliides hut two organs, the feathers
a i d tlie splceii, each of which rises to a maximum after hatcliiiig, but d o s c percentage remains greater than tlie hatching
pcirceiitage at maturity, iliid, d ) those pitrts wliicli rise t o
tlicbir maximum a t maturity.
3. Tell systems a i d organs i i i the chickeii have their maximum percentage at time of hatching. This sliows that more
oi-gaiis in tlic c4iick develop earlier than in tlie rat, due probaldy to the more active aiitl iaclcpeiitlent life of the chick immediately after liatching.
(a)
POSTNATAL G R O W T H OF C H I C K E X
253
4. A comparison of the life-cycle in the chick and in man
sliom7s that the development of the chick increases in rapidity
when compared with the development of man, thus leaving
a relatively longer period of mature life in the chicken.
BIBLIOGRAPHY
DOXALDSON,
11. H. 1918 A comparison of growth changes in the nervous sys
tem of the r a t with corresponding changes in the nervous system of
man. Proe. Kat. Acad. Science, vol. 4, pp. 280-283.
-___ 1923 On changes in the ielirtive weights of the viscera an d other
rat. Am, Jour. Physiol., vol.
organs from birth to maturity-albino
67, pp. 1-21.
JACKSON, C. M. 1913 Postnatal growth and variability of the body an d of the
various organs in the albino rat. Am. Jour. Aiiat., vol. 15, pp. 1-68.
JACKSON,
C. M., AND LOWREY,
L. G. 1912 On the relative growth of the
component parts (head, trunk and extremities) and systems (skin,
skeleton, inusculature a n d viscera) of the albino rat. Anat. Rec.,
vol. 6, pp. 449-474.
1908 The ratio between heiirt-wright an d body-weight in various
JOSEPH, D. R.
animals. Jour. Exp. Med., vol. 10, pp. 521628.
LATIMER,
H. B. 1921 The growth of the organs and systems of the single-comb
White Leghorn chick. Anat. Rec., vol. 21, p. 70 (abstract).
1923 The growth of the skeleton and some of the individual bones
of the single-comb White Leghorn chicken. Anat. Rec., vol. 25, p. 139
(abstract),
1924 Postnatal growth of the body, systems an d organs of the
single-comb White Leghorn chicken. Jour. Ag. Research, vol. 29,
pp. 363-397.
1925 The postnatal growth of the central nervous system of the
chicken. J o u r . Comp. Neur., vol. 38, pp. 251-297.
EIDDLE,
OSCAR, AND FREY,
PAUL192,5 The growth and age involution of the
thymus in male and female pigeons. Am. J o u r . Physiol., vol. 71,
pp. 413-429.
SCHNEIDER,
MARGARET, AND DUNN,L. C. 1924 On the length and variability
of the bones of the White Leghorn fowl. Anat. Rec., vol. 27, pp.
229-239.
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