Paper - The intra-uterine growth-cycles of the guinea-pig

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Marion Read J. The intra-uterine growth-cycles of the guinea-pig. (1913)

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This historic 1913 paper by Marion Read describes guinea-pig intra-uterine growth.


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The Intra-Uterme Growth-Cycles of the Guinea-Pig

By J. Marion Bead.

(From the Kudolph Spreckels Physiological Laboratory of the University of California.)

With 2 diagrams.


Eingegangen am 5. November 1912.


Archly f. Entwicklungsmechanik. XXIV.


The idea was expressed by LOEB *) in 1906 that some of the phenomena acompanying the early stages of development suggest 'that gr.o/w-i^ .tpayl be determined by an autocatalysed chemical reaction. He,, is jnclined to. believe that cell division in the developing egg ceases wBen: jfo-.^'atio of nuclear to cytoplasmic material reaches a certain limit, and expresses the belief that This ratio is determined by the laws of mass action and equilibrium . Following up this idea, ROBERTSON 2 ) and OSTWALD S ) published almost simultaneously in 1908 their investigations showing the great similarity between growth curves and the curves expressing the relationship between time and amount of transformation in a monomolecular autocatalytic reaction.


The work of numerous investigators has rendered available a large amount of data upon the growth of plants and animals of various species. Especially accurate data upon the growth of man have been accumulated by the British Association Anthropometric Committee and by QUETELET in Belgium. It was these data in addition to those published by DONALDSON 4 ) upon the growth of rats which ROBERTSON 5 ) chiefly utilized in illustrating his thesis.

) J. LOEB, >Dynamics of Living Matter.* New York 1906. p. 56 et seq. 2) T. B. ROBERTSON, Arch. f. Entw.-Mech. Bd. 25. 1908.

3 ) Wo. OSTWALD, Uber die zeitlichen Eigenschaften der Entwicklungsvorg'ange.* Vortrage u. Aufs. iiber Entwicklungsmech. d. Organismen, herausgeg. von WILH. Roux. Heft 5. Juli 1908.

4 ) DONALDSON, BOAS Memorial Volume. New York 1906. p. 5.

5) T. B. ROBERTSON, Joe. cit.


Mammals seem to have furnished the greatest amount of accurate information which we possess upon this subject, for it is an easy matter to weigh a mammal at birth and at stated times thereafter and thus to ascertain its increase in weight, which is the best measure of the growth of the whole organism. From information thus obtained, however, we get no idea of the rate of growth before birth. A curve representing this period of growth is in many respects the most important, for, if obtained, it would show the beginning of growth, the changes following upon fertilization, that is to say, the actual starting point of the reaction.


OSTWALD *) published curves showing the intra-uterine growth of the human foetus. These curves were constructed from the data of His and TOLDT in which length was taken as the measure of the rate of growth. OSTWALD also showed a curve of the prenatal growth of man based upon the weights obtained by FEHLING. Such data must, of necessity, be limited in number and consequently be insufficient for generalization, although OSTWALD'S curves are remarkably smooth. So far as I am aware, this is the only information we have concerning the intra-uterine growth of any mammal.

I have observed that curves constructed from the daily weights of guinea-pigs during pregnancy were not straight but somewhat S-shaped. MiNOT 2 ) in his exhaustive work on growth gives a table of the weight changes of pregnant guinea-pigs. The curve constructed from his data so nearly resembled the one I obtained that the possibility occurred to me of utilizing these data for the purpose of following the course of intra-uterine growth.

That the guinea-pig is particularly suited for work upon this subject is shown:

1) In that the ratio of the weight of the litter to that of the mother is very high, the average weight of a litter of three being about 225 gms. and the average weight of the adult mothers about 740 gms. These figures give a ratio of nearly 1 : 3.

2) In that the small number in the litter is an advantage, for the weight of the unit organism is considerable, even after the weight of the litter is divided by the number born.


) OSTWALD, loc. cit. 2) C. S. MINOT, Journ. of Physiol. Vol. 12. 1891.


The ten cases considered herein were selected from eighteen or twenty available ones. They were chosen because they seemed to

be normal m every way. As far as possible adult mothers were chosen, and so no litters consisting of only one are included J ). The cases designated as Xj and Kj were first litters, however, containig three and two respectively. No cases were included in which the mother became pregnant immediately after parturition, thus nursingone litter while carrying another.

All of my animals were weighed every second day, so there is a complete record of the weights of all for the past fifteen months. Table I, column A, gives the weights of the mothers at copulation. Except in the cases noted under remarks the weight is that actually observed, recorded within twenty- four hours before or after copulation. In the four cases noted under remarks the weight in column A was raised to an average of the weights for a week or two preceding. In most cases the weight at copulation was very close to the average weight.

For the sake of comparison and as an aid to correct valuation of the results, I am publishing two tables. Table I gives the weights as they were actually recorded and Table II shows these weights again with six of them corrected as explained under > remarks .

It may be noted here while discussing the weights of adult guinea-pigs and the corrections I have deemed it advisable to make, that these animals display considerable variation in weight from day to day. In an adult guinea-pig of 650 850 gins, a variation of ten or twenty grams is not exceptional. MiNOT 2 ) says, In all the weighings there is necessarily an error . A positive error because the digestive tract, particularly the wide caecum, contains always considerable quantities of undigested material; moreover the bladder may hold a greater or less quantity of urine. A negative error because every illness, even a very slight indisposition and every injury such as a bite for instance, causes a greater or less loss of weight. The quantitative value of these errors is presumably not very great; they probably counterbalance one another to a certain extent in the averages which may be accepted as approximately accurate. Guinea-pigs are very sensitive animals and a very slight disturbance will cause considerable change in weight. At a recent weighing almost all of my animals had lost heavily due to the fact that they had been moved the day before from one animal house


) Immature mothers usually bear one in a litter. 2 ) C. S. MINOT, loc. cit.


Table I. Actual, observed weights.

A

Weight at copulation


B

Weight

just before parturition


B-A

Increase of weight during gestation


C

Weights of the young ones in the litter


(B-A)-C

Weight due to fat

placentae and growth of mother


Bern arks upon revision of weights, too high or too low


A 2


749


940


191


64, 67, 72


12


B is too low, average


of weights for 16 days


preceding parturition





is 952 g.


A 3


810


1042


232


69, 68, 76


29



B 3


760


1030


270


67,92


111



B 4


855


1110


255


80, 84, 97


-13


A is too high, average


of weights for two


weeks preceding co



pulation being 834 g.


C 4


750


1091 341


57, 82, 95


108


A is too low, average



of weights for 10 days


preceding copulation



being 770 g.


H 2


542


908


366


76, 77, 79


132


A is too low, average


of weights for two


weeks preceding co


pulation being 579 g.


Xt


560


881


321


64, 67, 70


120



Bpi


766


1090


324


72, 77, 79


96


A is too low, average



of weights for two



weeks preceding co


pulation bein^ 783 g.


Bp 2


772


1030


268


74, 75, 79


30


B is too low, average


of weights for a week


preceding parturition



being 1055 g.


K,


430


716


285


79,81


125



into another, a distance of 50 feet perhaps. The disturbance was sufficient to cause one of the animals to give birth prematurely (59 days) to a litter of three.

The low weight at copulation in the four cases under consideration I belive to be due to the excitement and muscular work which is always attendant when a male is put into the pen with a female. The chasing is often quite severe and continues for some time. Upon many occasions I have noted a loss of weight after copulation.


Table II. Observed weights and weights corrected.


A

Weight at copulation


B

Weight just before parturition


B-A

Increase of weight during gestation


C

Total weight of litter


(B-A)-C

Weight due to fat placentae and growth of mother


Remarks upon revision of weights, too high or too low


A 2


730


956


225


203


22


A observed (749) was








too high, average for





10 days preceding



was 731.


A 3


810


1042


232


203


29



B 3 '


760


1030


270


159


111



B 4


834


1110


276


261


15



C 4


760


1091


331


233


98


Though the average for



A is 770, I believe


it is a little too high








and that 760 repre







sents better the








weight at copulation.


H 2


575


908


333


234


99



X!


560


881


321


201


120



Bpi


783


1090


307


228


79



Bp 2


772


1045


273


228


45


The weight parturi







tion has not been








raised to the average








of 1055, for reasons








discussed in the text.


Ki


430


715


285


160


125



In only two cases was the weight in column B corrected and in both it was raised to approach an average for a week or two preceding. It sometimes happens that the mother becomes upset somewhat before birth and eats lightly, thus gaining but little or even losing weight just before parturition. In most cases there is a steady gain up to the time of birth so in the two which suffered a loss it seemed reasonable to correct the weight. It must be understood that in all cases in which the weight is corrected it has never been raised or lowered to reach the average, but a weight has been chosen between the observed and averaged weight.

In the third column of Table II the increase of weight during gestation is given. This is in every case greater than the total weight of the litter. The difference between these two figures (found


The Intra-Uterine Growth-Cycles of the Guinea-Pig. 713

in the fifth column) represents the weight of placentae, amniotic fluid and blood lost at birth, as well as the growth of the mother. The mother's growth can be obtained separately by getting the difference between the weight at copulation and just after delivery. A figure thus obtained however, would represent two kinds of growth, namely, 1) continuous growth of the mother, and 2) fat accumulated during pregnancy. This accumulation of fat during the period of gestation seems to be a general phenomenon and is especially to be noted in the case of the guinea-pig, the milk of which contains such a high percentage of fat 1 ). For our purpose, we will disregard as far as we can, everything which is not growth of young in utero; this is represented by the value in the fifth column of Table II.

Table III is an illustrative page of the calculations showing the figures for A 2 , Bp 2 , and K t . The weight of the mother on every second day is placed in the first column and in the second appears the increase at each period over the weight at copulation. The last value in the second column corresponds to that in the third column of Table II.

Since we are concerned here with the increase in the weight of the litter only, it becomes necessary to eliminate the growth due to placentae and fat accumulated by the mother, in short, everything not representing the growth of the litter. We have only one determination upon the weight of the litter itself, that is, its weight just after birth. The difference between the weight of the litter and the total increase in the mother's weight during gestation is the value representing all increase in weight other than that of the litter. But this extra weight has accumulated along with the young in utero, so in eliminating it we must distribute it over the whole period of gestation. In order to eliminate this weight justly and to distribute it proportionally throughout the whole period, the following method has been adopted. A horizontal line was ruled off on coordinate paper. It represented by its length the number of days of gestation, each day being represented by one space on the paper. At the right end of this line a perpendicular was erected which corresponded in height to the value in the fifth column of Table II. Each space represented one gram. A right-angled triangle was formed when the free ends of the horizontal and perpendicular lines were joined by a straight line, which formed the hypotenuse. The distance

) J. MARION BEAD, Observations on the suckling period in the guineapig. University of Cal. publications in Zoology. Vol. 9. pp. 342, 343.


714


J. Marion Read


Table III.

Illustrative page of calculations, showing complete figures obtained from three of the ten litters utilized.


Days after cop.


A 2

Weights of mother during pregnancy


Increase over weight at copulation


Corrected for weight of placentae fat and growth


Bp 2

Weights of mother during pregnancy


Increase over weight at copulation


Corrected for weight of placentae fat and growth


Ki

Weights of mother during pregnancy


Increase over weight at copulation


Corrected for weight of placentae fat and growth


Three in the litter


Three in the litter


Two in the litter



730





772





430





2


730




776


4


3


453


23


19


4


757


27


25


785


13


11


433


3


- 4


6


757


27


25


785


13


10


449


19


8


8


760


30


27


785


13


8


455


25


10


10


747


17


14


790


18


12


456


26


9


12


755


25


21


778


6



463


33


13


14


781


51


47


800


28


19


480


50


26


16





785


13


3


490


60


32


18


782


52


47


800


28


17


486


56


25


20


777


47


41


792


20


8


485


55


20


22


779


49


42


820


48


35


500


70


31


24


782


52


45


880


108


93


509


79


35


26





821


49


33


511


81


33


28


788


58


50


860


88


70


512


82


30


30


813


83


74


868


96


77


617


87


32


32


826


96


86


840


68


57


519


89


28


34


846


116


106


878


106


84





36


848


118


107


886


114


90


570


140


75


38


870


140


128


895


123


98


584


154


85


40


875


145


133


930


158


132


576


145


73


42


883


163


140


913


141


114


580


160


74


44


915


185


172


927


155


127


585


165


75


46


908


178


164


924


152


123


592


162


79


48


918


188


173


956


184


153


618


178


91


60


944


214


199


1000


228


196


624


194


103


52


950


220


204


1007


235


202


629


199


103


64


960


230


213


1000


228


197


640


210


110


56


960


230


213


1020


248


212


655


225


120


58


985


255


237


1020


248


210


664


234


125


60


932


202


184


1010


238


199


668


238


126


62


940


210


191


1040


268


228


680


250


134


64


935


205


185


1040


268


226


684


254


135


66


945


215


195


1030


258


214


717


287


164


68


955


225


203


1045


273


228


715


285


160


The Intra-Uterme Growth-Cycles of the Guinea-Pig.

v

from the horizontal line to the hypotenuse along the ordinates, increases as we pass from left to right, and approach the perpendicular line whose length represents the weight increase during gestation, which was due to other factors than the weight of the litter. The length of each ordinate (distance between the base and hypotenuse) represents the increase in weight which is in excess of the litter's weight on that day, just as the length of the perpendicular forming one side of the triangle represents the difference at birth between the total increase of weight during gestation and the weight of the litter. The length of every second ordinate (i. e. every second day) was obtained, and this figure subtracted from the weight for that day in the second column of Table III. The remainder obtained was set down in the third column of Table III. It represented the weight of the litter on that day, the last figure in the column being the total weight of the litter at birth. This correction was made in all ten cases. The results are tabulated in Table IV.

This method of eliminating the weight of the deciduae, growth of the mother, and the accumulation of fat by the mother during the progress of gestation is undoubtedly open to criticism. It seems, however, to be the only feasible way of doing it and although there are doubtless errors involved, still the essential point which I believe that my data establish is the S-shaped form of the curve of growth in utero. Now a brief consideration of the probable effect of the above interpolation upon the form of -the empirical curve shows that the method employed, far from exaggerating this result, would tend to mask it for the following reasons.

1) It is reasonable to assume that the growth of the placentae and other foetal membranes will keep pace with the growth of the embryos and follow the same curve which would represent their growth. In assuming that the rate of growth is constant, as we have in the method of eliminating their weight, we tend to make the curve of the embryo's growth a straight line and thus straighten out any curved lines which may rightfully be a part of it.

2) What has been said regarding the deciduae may very well be true also of the fat accumulated by the mother during pregnancy. In the light of our present knowledge of hormones and the part they play in life phenomena, especially those connected with reproduction, we may well assume that this accumulation of fat is controlled by internal secretions whose amount and activity in turn are controlled by the growing embryos in utero. In eliminating this fat as if it


716


J. Marion Kead


Table IV.

Intra-uterine growth of ten litters and the growth of an individual represented by an average.



A 2


A 3 B 3


B 4


C 4


H 2


Xt


Bpi


Bp 2


K!


No. of young


Total weight


Average weight


No. in litter


3


3


2


3


3


3


3


3


3


2






















2




17


15


34


-3


16


5


3


19


22


106


4.8


4


25


21


11



74


4


28


9


11


-4


25


179


7.1


6


25


3


36


12


53


11


32



10


8


25


190


7.6


8


27


7


47


8


54


28


29


3


8


10


28


221


7.9


10


14


33


51


4


60


17


49



12


9


25


249


9.8


12


21


19


30


3


37


38


31




13


22


192


8.7


14


47


10


30


11



19


40



19


26


22


202


9.2


16



24



20


58


36


38



3


32


20


211


10.5


18


47


32


43


32


55


49


48


12


17


25


28


360


12.8


20


41


30


23


27


52


36


59


7


8


20


28


303


10.8


22


42



36


43


44


35


22


13


35


31


25


301


12.0


24


45



46


28


20


37


18


25


93


35


25


347


13.9


26



45


43


62


62


63


61


25


33


33


25


427


17.1


28


50


42


49


78


64


79


55


24


70


30


28


541


19.3


30


74


71


61


48


66


69


82


44


77


32


28


624


22.4


32


86


57


76


79


74


93


103


34


57


28


28


687


24.5


34


106


66



64


109


107


119


54


84



24


709


29.5


36


107


98


103


98


98


102


103


62


90


75


28


936


33.4


38


128


101


98


158


106


114


119


45


98


85


28


1052


37.6


40


133


78


100


135


167


132


155


79


132


73


28


1164


41.5


42


140


112


117


125


158


113


157


70


114


74


28


1180


42.1


44


172


141


133


136


157


143


167


87


127


75


28


1388


47.8


46


164


131


120


156


165


170


185


96


123


79


28


1389


49.6


48


173


147



145


155


193


173


123


153


91


26


1353


52.0


50


199


154


129


188


164


177


167


124


196


103


28


1601


57.1


52


204


158


136


192


154


186


163


126


202


103


28


1627


58.1


54


213


192


150


189


145


208


160


115


197


110


28


1679


60.0


56


213


205


126


221


152


210


158


130


212


120


28


1747


62.4


58


237


180


146


220


162


218


154


165


210


125


28


1817


64.9


60


184


175


167


245


198


225


146


180


199


126


28


1845


65.8


62


191


145


159


234


184


254


173


178


228


134


28


1880


67.1


64


185


174


143


240


186


246


202


205


226


134


28


1941


69.3


66


195


179


159


256


203


237


204


203


214


164


28


2014


71.9


68


203


203


159


261


233


234


201


228


228


160


28


2110


75.4


The Intra-Uterme Growth-Cycles of the Guinea-Pig. 717

increased at a constant rate, we again tend to make the growth curve of the young more nearly resemble a straight line.

3) The hypotenuse of our triangle resembles more closely the growth curve of the mother during the gestation period, for by this time puberty is passed and the growth curve of the mother is approaching an asymptote and is nearly rectilinear.

A few corrections have been made by interpolation in the weights of the pregnant mothers in cases where all the animals were heavy or light due to over- or under-feeding. But this was done only when the difference exceeded twenty grams. In Table IV only 19 out of 314 figures have been thus corrected.

Turning now to the consideration of the curve of intra- uterine growth thus obtained (Fig. 1) certain features of it demand careful attention. The first part of the curve representing the first four days of gestation is not significant of the growth of the fertilized ova but represents the rapid return of the mother to normal weight after the loss occasioned by chasing and copulation. The dotted line, therefore, probably represents the correct course of growth for this period. Although the most rapid cell division and relatively the fastest rate of growth, occurs in the early cleavage stages, still such growth will not be perceptible by the means employed in obtaining this curve. So we should not expect a very rapid increase during the first eight or ten days; for implantation of the ova does not take place till seven days after fertilization 1 ). The slight increase in weight shown may be due to the commencement of the accumulation of fat or to other physiological processes in preparation for the coming pregnancy; but this cannot be counted as growth of the litter in utero.

That portion of the curve from ten to sixty days closely resembles other growth curves which represent one cycle of growth. It appears probable, therefore, that one cycle begins at the fertilization of the egg and ends a week or ten days before birth, at which time (or before) another cycle begins and continues on after birth.

In Table V are to be found the weights and average weights for twenty days after birth of the same twenty-eight young whose growth in utero is represented by the first part of the curve. The curve constructed from the averages in Table V is added to the curve at the 68 day ordinate. There is a slight loss of weight at birth


l ) GROSSER, Vergleichende Anatomic und Entwicklungsgeschichte der Eihaute und der Placenta.* Wien u. Leipzig 1909. S. 162.

Archiv f. Entwicklungsmechanik. XXXV. 47


718


Crams


J. Marion Read Fig.l.


~~^~ 20 30 40 50 60 70

Intra-uterine growth of the guinea-pig. (Constructed from data in Tables IV and V.)


The Intra-Uterme Growth-Cycles of the Guinea-Pig.


719


Table V.

Weights and average weights of the twenty-eight young under consideration, for twenty days following birth.



Age in days




1


2 3


4


6


8


10


12 14


16 18


20





1






!




G


67


66


66


67


70


75


82


87


97


108


110


116



H


64


64


63


64


70


77


85


93


105


111


116


123



I


72


71


70


72


75


84


87


95


107


119


122


133



W


76


79


82


89


91


102


112


125


122


128


137


133


136


Aa


68


69


74


78


80


91


100


107


118


119


125


132


134


Ab


69


61


63


67


70


78


86


95


102


107


114


118


122


R


92! 96


101 101





136


144


162


168


180


182


S


67


72


79 81





114


124


135


139


160


152


Ca


95


93


96


99


102


109









Cb


57


56


61


61


67


71


84








Cc


82 ! 76


80


84


88


98


111








M


79


77


82


84


93



108








N


77


75


77


80


84



100


130


134


139






72


72


73


78


84



110


136


147


161


166


180



Bpa


74


74


77


84


87










Bpb


75


75


77


85


89


100









Bpc


79


79


82


90


91










V


67


63


65


68


74


79


91


102


108


127


140


142


160


K


70


66


69


71


74


80


94


106


108


127


138


138


155


L


64


60


63


66


70


77


86


95


99 ; 114


130


133


147


Ea


81.


77



83



99


107


119


123 132


144


163



Kb


79


74



81



98


106


115


117 119


132


140



Ba


80


79


86


94










Bb


84


84












Be


97


95


101


110










Hb


76


77



88










He


77


78



84










Hd


79


81



89










Number















of obser

28


28


22


27


18


15


16


15


15


15


14


14


8


vations















Total


2110 2087 1685


2188


1459


1318


1549


1655


1755


1908


1881


1981


1177


Average


75.4


74.6


76.6


81.0


81.0


87.8


96.8


110.3


117.0


127.2


134.3


141.5


147.1


47*


720


J. Marion Read


which is characteristic of almost all mammals, but the animals pick up in two or three days and the curve continues on at the same inclination as the line representing the intra- uterine growth of the last eight or ten days before birth. This fact would seem to indicate that the figures and curve representing the intra-uterine growth, although obtained indirectly, have some degree of accuracy.

OsTWALD 1 ) in discussing the curve showing the growth of man says, It is worthy to note again the continuity of the weight changes during the last foetal month and the first years of life. The well known loss of weight of the new born during the first days of life is so insignificant that in comparison to the remaining

Fig. 2.


30


20


10


Per Cent



10 20 30 40

Curve of pregnancies resulting in abortion {constructed from data in Table VI).

weight changes of the development of man it scarcely needs to be considered .

It is interesting to note that, as far as we can learn from the data so far obtained, the birth of both guinea-pigs and man does not take place at the juncture of two cycles. This is especially interesting in the case of the guinea-pig, which is born in a very mature state 2 ). The period of gestation is very long when we compare it with the gestation period of other rodents. This has led one investigator 3 ) to venture the belief that in some remote period in its evolution the guinea-pig was born in a less mature state, such as


) OSTWALD, loc. cit. 2 ) READ, loc. cit.

3 ) ABDERHALDEN, Text-book of Physiological Chemistry, p. 371.


New York 1908.


The Intra-Uterine Growth-Cycles of the Guinea-Pig.


721


Table VI.

Per cent of weight gained or lost, during the period of gestation, by five guinea-pigs which gave birth to dead, premature litters.


Days

after copulation


Y

7 Born


C

5 Born


A

3 Born


HA

1 Born


K

5 Born


Average per cent increase









2


5.8


5.1


0.9


3.0


4.4


0.0


4


2.8


3.0


5.7


4.4


1.3


2.7


6


0.7


0.2


3.6


0.0


-4.7


-1.5


8


0.7


4.7


-2.1


-0.8


2.9


1.1


10


1.0


4.2


0.5


1.0


0.8


1.3


12


0.0 | 1.0


2.0


-1.2


-1.6


-0.6


14


4.0


4.9


-2.9


2.1


0.6


1.5


16


2.5


2.0


-0.7


0.3


0.6


-0.1


18


0.5


-0.2


0.4


-7.4


2.2


1.7


20


0.0


5.1


0.3


1.9


1.2


1.7


22


3.1


1.3


2.7


0.1


-2.0


0.5


24


1.5


-2.0


-4.3


1.1


3.4


-0.2


26


-3.6


0.7


1.6


-1.8


2.2


-0.1


28


2.0


1.2


0.9


5.0


3.8


2.5


30


1.8


3.2


2.0


1.9


4.3


2.6


32


4.8


-0.7


-1.0


4.2


1.5


1.7


34


2.5


2.8


3.4


1.1


1.8


2.3


36


2.8


2.4


6.0


4.0


2.8


36


38


2.2


0.1


4.6


0.6


0.3


1.7


40


1.5


2.2


3.3


1.2


1.3


0.6


42


3.4


1.0


3.0


1.8


1.8


2.1


44


-0.1


0.7


1.4


1.0


3.0


1.2


46


1.0


2.6


3.2


-1.6


3.5


1.7


48


1.7


3.0


4.4


0.3


4.1


1.8


50


5.2


2.0


0.0


1.5


7.6


1.2


52


8.0


0.0 0.2


0.0


0.0


-1.6


54


0.1


-1.0


4.9


-4.2


7.3


-3.5


56


3.6


-1.6


-4.2



-53


-1.9


58


0.4


-4.3


4.6



0.9


0.4


60


1.0


25





-0.7


62


1.0


0.4





0.3


64



0.5





-0.5


that in which rabbits, mice, and rats are born. If such were the case, the young must have been born before 50 days, for the two cycles seem to join or overlap between 50 and 60 days. This period seems to be a critical one in the development of the foetus. Inspection of the weights of mothers which gave birth to dead young


722 J. Marion Read

shows that these mothers lost weight rapidly during this period. Table VI gives the percentage of weight gained or lost every second day by five mothers who gave birth to premature, dead litters. Fig. 2 shows the curve constructed from this data. A distinct loss of weight is shown after 50 days. Whether or not this phenomenon has any connection with growth cycles, it is impossible now to say with certainty. But it is possible that the death of the young in utero may be due to a failure of the second cycle to connect properly with the first. The fact of the death in utero at this period is undeniable and I mention it as possibly having some significance and bearing upon this and perhaps other questions of intra-uterme development.

In conclusion, I may say that I realize fully the fact that the data upon which the curve has been constructed have been obtained indirectly and that more accurate data could be obtained only by the sacrifice of hundreds of animals. But as a first attempt to arrive at the truth in regard to the appearance of a curve representing the growth following fertilization, I it submit with the hope that it may serve as a starting point for further work.


Summary and Conclusions.

From the facts and figures set forth and discussed in this paper and from the appearance of the curve constructed from the data, it seems reasonable to conclude that:

I. It is possible to obtain a curve showing the growth of embryos in utero by indirect means, i. e. by weighing the mother at regular intervals during pregnancy.

II. In the case of guinea-pigs, one cycle begins at fertilization of the ova and ends about 60 days after. Another cycle begins a little before the end of the first cycle and continues on after birth.

III. In both the guinea-pig and man birth occurs during the course of a cycle and not at or near the juncture of two cycles.

IV. The human young are born before the completion of the first cycle, while the guinea-pig completes one cycle and begins a second in utero. It is quite likely that this fact accounts for the advanced state of development of the latter animal at birth.


The Intra-Uterme Growth-Cycles of the Guinea-Pig. 723


Zusammenfassung,

Nach den in dieser Arbeit vorgebrachten und ero'rterten Figuren und Tatsachen und nach dem Aussehen der aus diesen Tatsachen konstruierten Kurve scheinen mir nachstehende SchluBfolgerungen erlaubt:

1) Es ist moglich, eine Kurve zu erhalten, welche das intrauterine Wachstum von Embryonen durch indirekte Mittel veranschaulicht, so durch regelma'Cig wiederholte Wagung der Mutter in regelma'Bigen Zwischenraumen wahrend der Schwangerschaft.

2) Fur das Meerschweinchen beginnt ein Zyklus bei der Befruchtung der Eier und endet ungefahr 60 Tage spater. Ein andrer Zyklus beginnt eine kleine Weile vor dem Ablauf des ersten Zyklus und dauert noch nach der Geburt an.

3) Sowohl beim Meerschweinchen wie beim Menschen fallt die Geburt in den Verlauf eines Zyklus und nicht in oder nahe an die gemeinsame Ablaufszeit zweier Zyklen.

4) Die Jungen des Menschen werden noch vor der Vollendung des ersten Zyklus geboren, wahrend das Meerschweinchen noch im Uterus einen Zyklus vollendet und einen zweiten anfangt. Es ist durchaus wahrscheinlich, daC dieser Umstand die Ursache fur das vorgeriickte Entwicklungsstadium des letzteren Tien, bei der Geburt abgibt. ((Jbersetzt y(m ^ WebImi . dt-)


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Inhalt des vierten Heftes.


Seite


HERM. JOSEPHY, Uber eine Doppelbildung bei einer Tritonenlarve. (Mit

1 Figur im Text und Tafel XIV) 539

C. M. CHILD, Certain Dynamic Factors in Experimental Reproduction and

their Significance for the Problems of Reproduction and Development. (With 3 figures in text) f 598

GERHARD KAUTZSCH, Studien iiber Entwicklungsanomalien bei Ascaris. II

(Mit 63 Figuren im Text und Tafel XV und XVI) 642

T. BRAILSFORD ROBERTSON, Further Explanatory Remarks Concerning the

Chemical Mechanics of Cell-Division. (With 3 figures in text) ... 692

J. MARION READ, The Intra-Uterine Growth-Cycles of the Guinea-Pig. (With

2 diagrams) 708

I. IZIKSOHN, Uber die gestaltliche Anpassungsfahigkeit des Froschherzens

an groCen Substanzverlust ?24

B. HANK6, tlber die Regeneration des Operculums bei Murex brandaris.

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Versuche an Tritonen. (Mit 6 Figuren im Text und Tafel XVIII

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RH. ERDMANN, Referate iiber Experimente an Protisten . 781

JENNINGS, H. S., Assortative Mating, Variability and Inheritance of Size

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of Infusoria 783;

WOODRUFF, L. L., Evidence on the Adaption of Paramaecium to different

Environments 783]

WOODRUFF, L. L., and BAITSELL, G. A., The Temperature Coefficient of

the Rate of Reproduction of Paramaecium aurelia. ........ 783]

GRUBER, K., Biologische und experimentelle Untersuchungen an Amoeba

proteus

PEEBLES, FL., Regeneration and Regulation in Paramaecium caudatum ERDMANN, RH., Depression und fakultative Apogamie bei Amoeba di ploidea _.

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