Attelliinn is <lirectecl to the ]JHUcity of infmuwtiou 1·eganliug prenatal gro1dh of clome,;ti<·atP<l JJJalllllJal" aud to tlw fad that llllll"h of the ant.ilable knowledge is rendered rmtdically valuele,;s through lack of accurnte cle•finitioit. 'l'ht> im lJortmlc<> of accurate standards for ageillg foetu,;p:-; is stres~ecl. The present inve;;tigation aims at provilling ~ueh stnuuanls ftn· the )lerino sheep. In ad<lition, durillg the course of the \York 1·aluable data have been collected eon<·erning·
thosP maternal ~ystem,; "·hich are chiefly n~soeiatPcl in tht> relwo- ductive proress, i.e. the genitalia, tile enJocrines fiJHl t·he manJJll<ll".'.
glands. \YlJereY<-'1" possible. changps of a cpmlitati.ve natun• have been desni.betl in <ldnil, "·bile ttu:mtitative rlnta h:we he<>ll snb.iedecl to .~tntistical :m:tl~ ,;is.
In the ,;heep it is found tha.t, ''"it·h the exception pf the Fallopian tube,;, the entire genital tr:td underg-oes exten~i,·e enlargemeut <luring pregnall<·.\". bt the horns and the body of the ntenu; :t ,;ignificant enlnq.!.·enJent is e1·i<lent sooner than in the Yagina an<l the <"<>rvix.
Vi'herP:1s the fontiPr han· to carry the <lPYel;tpiug foptal sy"tP.n.
wcrea~e in the lntit•r m<>rely anticipate~:> the neP<ls of parturitinH . .In all tht>~e organs the enlargement ohserve<l is the re.sult of active g-rmdh of thP rrgion:;; cmlcerne<l, not of mere p:t,;siYe stretchiJJg.
B~· about mid-term the placenta has rea<·he<l its maximum dE>Yelopment:. Aftt"J" this there io; <1 fnll in "·eight, while the in eli vidua I eoty le<lon s tPn <1 i o he come fb ttenecl. Through on t pregnancy the ''"eight of the foetal memhrnnes innen~es steadil~·.
Tlte total Yolmup of foetal flnid i.unf'ases rapidly until the thinl month, n·mains pradicall~· unchange<l dnring the fourth, nlHl then again in<TP:tses. The first increase is the n·~ult of 1 apid al"cnmulahon of amniotic fluitl, IYhile the second is <luP entirely to the allantoic fluid; for <luring the second half of gestation tl1e ,:Jlume of amniot.i<
fluid become.~ <le<·Jea~e<l. During thf' fom·th moutl1 a hnlan<'e i,;
nttainecl between allantoic inerPnse and amnioti<" <lenease. This flattPning of the curve i,; reflecte<l in lll<H-;t of the 11·eight,; and measure- nwnts of the uteru~. Although S]Jecific graYiiy an<l !tyclrog'PJJ-ion
<·oncentration of the fiuid~ \\"Pre <·on;;i<lered, no imporhlllt ehanp:es
IT ere cl etertP<l.
l'he y;pight of the matPrnal mammary gland lwg-ius to innea,;e iu the fourth month of gestation, bllt the major portion of the
lllc·n~a,;e necurs onl:r in the htst. month. The wa.!.ery secretion ub,;PneJ at mid-term ch:mge~ gratlually into the yellowish honey-like f'holostral milk.
Heg·arrling tlle maternal en<lorri'le glanos it i~ eonduc1erl that ns a. result of large individual varint.ions uo significant manoseopic ch::nges can be demonstrat.ed. For S1H'h studies Yery large groupo: of ammals woulrl he necessar~·.
G37
J'IIBNATAL (X!W\\.Tll L'\ THE MELUC\"0 :-;HEEl'.
vVith referenc-e to the foetus it is found that g-rowth 1oth iu weight and in length follo"·~ a double parabolic trend represented by the formu Ia
Loge Dimension = a + b Loge Age
+
c (Loge Agc)2.The coefficient of nu·iation for "·eight is o1·e1· :ZU per ceu L, whe1·eas that of the moHt satisfactory lengtl1 me<tscuement (lt>ngth of th<·
1·Prtebral cohnnn) is unde1· 4 per t•eul.
The percentage gro1dh-rates of both length ancl 1n"ip:b t deGrease ,;teadily and GontinuouBly through011t prenatal life. TheTe iB Ito
eYirlence of abrupt " l1reaks .. in these rates.
The weight-length Tatio of the gnmiug foetus follo11·s a ;-;imple logarithmic treutl. The coefficient of ntriation is high, Jwmely <~Lout
17 per cent.; lwnce this r:t!io lwc; little 1;dne as au iu!lex ol age. lu LOonnectiun 11itiJ regiomd grmdh it is fouutl that IYitll the exLOeption of length of the nt:d~ ("·hich is highly 1m·iahle) all tl1e dimensions considen~cl arP ca pa hle of 1·epTeseuta tioH hy paraholuP such as deserihed for gwwth of tl1e entire body. From a consideration of the percentage grmdh-rates of these tlimeu,.;ion~ tb f' t h emy i,;
formed that changes in tlw proportions of the gTo\Ying foetus are the result of <liffenential rate:.; of retardation of rPg-imtal gTowth. The degree of retardation in any 1·egiou appears to l)e pmportioua 1 to the lapse of tinll' since• the im·Pption of gn11dh in tl1at rPgion.
In oue comprehe11sive table are :.;et out the total, trend and residual correlation eoefficieutc; for each p<lir of dimension,;. ln all ins tan ees the total conela ti on is hi g·h ly :.;ignifiean t, hut onl .1·
between doc;e]y 1·elated rlimenc>ions i,.; there a "ignificaut residual correlatio11. Thus in most in:.;tances the high total correlation is tlue almost entiTely to the r·.onmlOII growth-trend.
As the objed of the work is to pnwide ageing standards, details a rH furnished as to the manner in which the above knmdeflg·e is to be applied. Speci<tl meution i:.; made of a ::;imple normograph so eonstructed as to allmY of the straightfor11·ard Teading of nge from one or mon~ measure<l dimension::;.
lu a supplementary iS!~dion are conc;idered the relation bet11·eeJ1 the pregnant horn of the uterm; anrl the situation of the corpus luteuru, and t1J e growth of the entire foetal system. In t:onnedion with the fonuer it is concluded that there i~:> a significant tendency for the foetus to he carried in the horn on the ~a me si tle a;; the ovary eoutainiug the eorpus luteum. The num hers of foetuses LOarried in ear:h horn do not vary significantly, neither is theTe eYidenee of any tendency towards migration of thP onun in one
~ peci a 1 eli recti on.
Knowlt>dge of the \Yeight of the foetal s.v,;tem is of importance to \Yorkers wishing- to ac1just the li1·e \\·eights of pregnant p\\·es. In this investigation the nett weight of the ewe (i.e. gross weigM less weight of foetal system) is fouml to have no significant effect on the weight of the foetal syste!ll. Hence an eqnation i:.; presented i11 which tlw weight of the foetal ,;;-·~tem (i.e. tlw corrt>ction to
538
.f. ·11. 1.. ( 'I.OI·:TE.
be applied) i~; ginn in terms on I~· of the ]engt h of gt>~ta tion. l-1 O\Y- ever, a~ the coefficient of variation is over 26 per cent., t1J e conedi ou must be regarded as Yer:v approximate.
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MJNOT. C. S. (HJ08). Cit., Brotly (1!)27a).
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