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The incidence and size of the moderator band in man and in mammals.

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T H E INCIDENCE AND SIZE O F THE XODERATOR
BAND IN MAN AND I N AIAllIlllALS
R. C. TRUEX AKD L. J. WARSHAIV
Dcpartmeitt of Aiiato?iig, C o l k g e of Physzcaans and Surgeoits, C o l i m b i a Unizeisitg,
New Tork C i t y
THREE FIGURES
The term moderator band was probably coined by King
(1837), and given to that interesting muscular bundle which
lies in the right ventricle of the niammalian heart, extending
between the muscular portion of the interventricular spetum
and the base of the anterior papillary muscle. Since this
structure presuniably prevented overdilatation of the right
ventricle during diastole, he called it “the nioderator band of
distcntion. ”
I n the literature one now finds reference t o this fascinating
anatomical entity under a variety of terms, e.g., inferior arcade
of Parchappe, ansiform band of Poirier, arched fascicle of
Testut , and ti-abecnla supraventr icularis of Ret zer . Taw a r a
(’06) demonstrated that in the sheep this band contained the
riglit branch of the a-v bundle and designated it as simply
“muskelbalken” or muscular band.
The coniparative anatomy and various relationships between the moderator band and papillary muscles have received considerable attention (King, 1837 ; She, 1874 ; Brown,
1889 ;Testut, ’05 ; Tnwara, ’06 ; Keith and Flack, ’06 ;Horaiid,
’08 a ; Retzer, ’09; and Argaud, ’12). It is interesting to note
that moderator bands have also been described as existing
in the left ventricle (Huchard, 1893 ; Browicz, 1896 ; Turner,
The authors wish t o express their appreciation to the Departments of Pathology,
Pharmacology and Phgsiology of the College of Physicians and Rnrgeons, Columbia
University for their cooperation in plaring fresh human and animal specimens
a t our disposal. We are indebted to Mr. C. E. Kellncr f o r his life-like drnvings
of spceirnms used i s illustrating this communication.
361
362
R. C. TllUEX A N D L. J. WABSFIAW
1893 and 1896 ;Rolleston, 1897 ; Keith and Flack, '06 ; Horand,
'08 b ; and Monckberg, '08). The latter bands, usually of
small caliber, are abcrrarit fascicles of Purkiiije fibers derived
from the left branch of the a-v bundle, enroute to papillary
and rciitricular musculature.
In the literature cited above, most all of the mamm n1'la11
liearts have been examined in ascertaining the structural
variations in the papillary muscles. No investigation has been
made to determine the incidence of the moderator band in
different animals othcr than man.
Keith arid Flacli ( '06) have described a thickened sept2al
trabecula in the liumaii hcart, which is only slightly separated
from the rcst of the septa1 musculature. This trabecula, having the same relationships of the moderator band in the
slieep's heart, is tlie poorly developed moderator band of man.
Accoidiiig to these authoi-S, the classically described nioderntor baiid does not exist in the l i u m ~ nheart.
IIorand ('08 a ) quotes that Testiit has found a hand in
70 t o SO(/-, of linnian hearts. A fnrtlicr studv of 120 human
liearts by IIorand, led him t o cls~ssifytlie ever presciit band
a s of three primary types. Transitional stages between the
three types are frequcntly observed.
1. Faisceaii arqu6 libre.
Very rare in man (4%). Tlie free band may attach to
the base of the anterior papillaiy innscle, o r tlw anterioi.
wall above the papillary muscle.
2. Faisceau arqu6 partiellement libre.
Quitc comnion and is the classical type. The superior
border of the hancl is free, while the inferior bordcr is
partially blended with the septuiii. Tt inserts into the
papillary muscle, near thc junction of the scptum and
anterior wall of tlic right ventricle.
3. Faiswau a i q i i t compl6tcnient ac1liFrcnt.
Most comimon and frequent tppc. Both superior and
inferior horclers are complctelp acllierent to the septum.
Tlie band is r e r p thick and map clemonstrate pits or
iiiden t il t ions along its siipci*ior border.
In view of the above conflidiiig rcpoi*ts, atlditioiial iiiforiiiatioii sccrrid desirable, especially a s i*egaiatls tlic iiicideiicc
and size of this structure in ~iiwii.
1 l A \ T E R I A LhSD blETHOI ) R
This study w a s iiiadc hy exaniiiiiiig tlic fresli lienrts of
100 cats, 12 rliesiw nioiikeys, 1 2 dogs, 1 2 pigs, 1 2 slieep,
1 2 calves arid 1 2 heevcs. The 500 liunian Iicai*ts wci’c fiscd
niuscuiii spcciriiciis, and fresli hc:ii*ts es;iniinecl at autopy-.
111 determiiiing wlietlier ii true moderatoi- band was present
iii the i-ight ventricle, we classified arid measured only tliose
hands wliicli w e i ~entirely free from the septum in at least
1)ai.t of its c o u ~ x c . When the bniicl docs not exist as ti f i w
cord stretcliiiig f r o m septum to papillurp iiinsclc 01’ aiitci.ioi*
wall, it is iiripossiblc to distinguish clcfiiiitely between ;I ixcliiiieiitai>y baiicl and tliiclicned septa1 trahcculac (trn1)ecdac
cordis). T n our opinion, sucli cases (lo not possess 21 tiwc
haiid, siiice tlie aiitei*ior papillti1.y muscle arises froin tlic
jniictioii of the aiitei*ior veiitricular wall witli tlic septum
(fig. 3).
The points iisctl in measuring wlicii tlic lmiicl as pi.csciit ai’e
sliowii in figure 1. Tlie length of tlie band ( A R ) i.c~pi~xeiits
tlic distarice hetwceii the point wlicre it heconies aclheiwit to
tlie septum ( A ) , aiid its insertioii into the aiitci-ior pal)illai-?ninscle (B). The M-icltli ( a a ) repi-csciits tlie tliamctcr of the
h a r i t l in tlic iaegion of its grciltest tliiclriiess (hetweeii A a i d Fs).
Scptwl attacliniciit (A(’) is tlie distaiicc bctwecii the poiiit
w1ici.e the b aid fuses vitli tlie septum ( A ) , a n d tlie npes of tlic
i.iglit ventricle ( C ) .
Tlie cat left i t l i d iiglit s.eirtriculur walk were riieasuwtl iii
their thickest poiiit. This measmreirient is usually tlir.ougli
tlie fleshy myocardium just infci.ior to tlie fibrous i-iiig of
each vciitriclc.
a l l measuiwiiciits w e i made
~
with a pair of delicate slimy
pointed calipers, nncl iwid by placing the calipers on ;I
standard milliriie ter sea le.
364
OTW IS1-1VATlOKS
Data obtaiiicd from ilicsc studies a i ~ shown
l
in table 1.
The iiieaii leiigtli, widtli aiid septa1 attacliiiieiit of tlie baiid,
mid tlic iiieaii tliiclriiess of tlic ventricles a r c all e~lwcsseclin
iiiilliiiietcrs. Range ( R ) is given iii each colmmi of tlic table,
lielow tlie riieaii baiid nieasur~nieiits.
hiiirvials arc i i ~ ~ a i i g eiii
c l tliis sei-ics iii nccoidaiicc with the
size and clevelopiiieiit of tlic 1icwi.t and nioclei~~toi*
haiid.
Gut. Fifty-one per w i i t of tlic Iicavts from tliis aiiiiiial liaci
f i w inodei*atoi. baiids. Tlic riiciiii liaiicl iiicvisureinerits wchre
4.8 iii lciigth, 3.0 in widtli, a i d scptal attxcliiiieiit 13.0. hleail
vciitriculai* thickii
was 7.7 oil the left a i d 2.2 on the riqlit.
J I o d e ? y . E’ortyoiic and six teiiths 1x1. cent of tlie speciiiiciis
I i a d niodewtor haiids. Aleail haiicl size was leiigtli - ,5.4;width
- 2.3 ; scptal attacliiiieiit - L5.0. The nieaii tliickiiess of the
left veiitricle was 8.0, and tliat of tlie 1.ig1it2.6.
3 01)
Noiikc~
12
12
300
Slleell
Pig
Calf
12
12
12
12
53
(R. 3-8)
3.0
(R. 2-6)
2.3
(R. 1-3.5)
0
0
0
284
(36.8% )
12
(100%)
12
(100%)
12
( 100%>)
12
12.i
(51%)
5
(41.6%)
( 1 00% )
4.8
(R. 3-9)
3.4
(R.3.<5-20)
20.4
( R . 15-24)
6.0
(K.1.3-14)
3.1
(It. 2-4)
13.0
(R. 11-21)
I .5.0
(R. 8-19)
I.1
2.2
8.0
2.6
0
13.0
4.2
39.1
(R. 15-72)
15.2
4.87
42.4
16.0
6.2
20.4
10.5
“5.5
11.2
38.0
17.0
(a.33-49)
23.0
4.2
,543
(R. 13-51)
( R . 1-i)
(R. 4 1 4 6 )
23..5
(R. 3 - 3 0 )
(R. 1-12)
(R. 38-66)
36.6
(It. “5-48)
9.0
(R. 2-15)
( R . 46-96)
4.4
--
.ii.S
74.4
D o g . KO nioderatoi. 1x111~1was found i n tlie twclve spcciesniiiiiied. Tt is intci*cstiiig to note, that all of tlicsc
lica rts Iiad tlirce ~r-clldcvelopecl papi1lai.y iiiusc1es, arising
pai’t of tlie septuni. 111 seven cases
directly from tlic low-c~~
t1iei.e u ~ i soiie posterior a i i d two aiiterior papillary muscles
of scptal o ~ i g i n wliile
,
in tlie i*eniaiiiin,q fire specimens t h e i ~
w a s m e anterior and two pohtei.ioi*pipillai-y ii~usclcs.A small
papillary niuscle of thc (wiius was always present.
Thc iiicaii tliiclmesses of thc. left arid riglit veil ti-icles were
13.0 aii(1 4.3 ws1)ectivc~ly.
iiiciis
366
.:1
C. TIIIXX A S D L. J. WAItSHAW
1ieurt.s were froin iiidividutils of 2\11 ages (8 weeks
to 85 years) regardless of SCX Tliosc spccimons demotistrating a free baiicl (SS.S./,) litid tlic followiiig incan iiioasurcmeiits : length 12.7, wicltli 6.0, septa1 nt.tachiiiciit 39.1.
Tlic extreme ranges iii btiiicl size (table 1) arc due t.o tlic
smtill Iicurts of iiift1iit.s on t.lic oiic huiid, arid diluted, hypertrophied lietirts o i i tlic othcr. Tlic stme ftictors accowit for
tlic wide cxcursioiis of rniigc in vciitricultir t.liickiicss.
111 t.hc liunitiii specirnciis, w1iei.e sampling w i s tidcquate,
the reiit.ricles wcsc 11ieasLil:cd d i c i i tlie b t i l i l W ~ both
S
prescilt
atid til)sciit. With ti hand pi*escnt tlie nict~nvc!lltlkltir tliickiiesx w\'tls 15.2 (13.. 8-35) on the left, t i i d 4.83 (K. 2-20) on the
ibiglit.. 111 h(?itl*tswithout t i moclemtoi: btiiicl, the incaii left
ventricular t1iic:kiicss wtis 15.9 (R. 6-26), t h t of t.lic! right
veiitriculc 4.87 (K. 1-13).
Tlic! ~oiiiptirisoii of veiitric?uliir tliickiiesses iii lieti rts possessing htiyids, mid thosc witlioiit this structure, show 110
significaiit clithrciicc.
Although 61ic developmiit uiid rcltit ioiisliip of tlic iiiodcixfor
band is subject to m a n y eomples vtirititioiis in cliffcrciit speciIIICIIS, figui-c 2 sliows it K typictil tippctirtiiice in nia.11.
As poiitt.ccl out 1 ) ~€lormid ('08 t i ) the baiicl niiiy insert
into citlicr t.lw btise of t.he tiiitci*ioi*papillary i~iusc*Ic,or
di i-cc+ly iiito tlie tiiitcrior veiit.ricii1ti.rwtill.
If ti tlcfiiiito niodci*at.oi*
huiitl is ii1)sciit i l l the liuniuii lieart,
tlic iint.erior papilliiry muscle iisiitdl>-Iit~st i joint oi'igiii in
the iil1glc foi*incdby tlie aiitci-ior rciit &iililr wall mcl niiisciih i * iiif crvciit ricwlar sept.um (fig. 3). ?'hick traheculne cstendlf.ti/iimz..
Fig. 2 Riglit vcntric*lc of 1iiini:in licnrt (with hypertrophy) slinwiiig R t.ypic:il
niodiv:itur b:ind :tiid :issoei:itcd striictiircs. h t . c r i o r wnll 11:ts l w i i mt :ind
reflwtcd upw:ircl. 1. Vcntriwkir siirf:ice of trieiispid v:ilw: tiutcrior c~isl).
4. C'liorda tencliiiciie. 3. Postcrior p:ipill:iry niusclc~. 4. l3:ise of antcrior p:ipiIl:iry
niiiscle. 5. Modiwtor Iinnd. 6. C r i s h supr:ircntriculnris. 7. Seini1un:iry valves
of pulnionnry artmy. 8. P:ipill:iry miisclo of conus. 9. Conus nrteriosus. 1.0. Cut
trabceulnc cordis lit jiinct.ion of nntcrior wnll and niiisculnr intrrvcntriciilnr
septiini. One-linlf lifc-size.. (C!:ise 135, ni:iIc 52 years).
Pig. 3 Right wiitricle of 1iuni:i n Iic.:irt, sliowing typicvil rippc.nr:iricc of the
:intc*rior p:y)ill;iry IIIIIM~IC,
w l i ~ w the modcrntor linnd i s :ihwiit. 1. Origin of
:interior papillary iiiiisele froni both :intt*rior \\.:ill :ind iiitervcwtrieulnr septiini,
i.c., jiiiic.tion:il origin. Two-tliircla lifv-niw. (C:isc. 112. fcni:ilo 35 ye:irs).
MODERA’COR BAND
367
368
Tt. C. TRUEX ASD L. J. WAUSHAW
ing 1)ctweeii the septum and niiterior wall in this region of
the right ventricle, rcncler the identific.ation of a c1istiiie.t hand
imp0ssiblc.
In only a few cttses with tlic baid al.)seiit, were we able
to find the antcrior ptipilltiry muscle arising solely from the
anterior vciitriculai. wa.11. 'l\Tlieii this unusual condition existed, t,lic origin of the pa.pilltiry muscle 011 the a.ilterior wall,
was iievcr more t.han 1 inch (25 iii~n.),from the junction of
septum and a.nterior wall.
Duplication of papilhry iiiusclcs in the right vcntricle of
man is not uncommoii. Two tind even three ttiitcrior papillarp
muscles, have Iccn observed tirising from the anteri.or wall of
n single specimen.
Sli.eap. All specimens ha.d a moderator lmnci, t.he mean
of' which were 20.4 in length, 3.1 in widt.li, aiid
mct~sni*ements
a septa1 tktta.c.liment of 42.4. Mea.ii vciitricular thictknesscs
wc1.e 16.0 on the left, and 6.2 on the riglit.
Pig. 'A moderator ba.iid was prosciit in all specimens, but
here as in the calf mid beef hearts, its development is cseeediiigly variable. It may be a loiig thread-like corcl consisting almost entirely of I'urkinjo fibers, or ttgain it ]nay be
very short and thick with ti prepoiideraiit amount of ca.rdiac
fibers. Such variations tire responsible for tlic cstrcmc ranges
giveii in tliesc t h e e aiiimnls.
Tlic nwan btind measurements in this aiiinitil wei*e 23.0 in
leiigth, 4.2 in width, and scpttil tittacliment 54.8. 3fenn veiitricular thickiiess wtts 20.4 in the left and 1.0.5in the right,
Calf.The hand wa.s present in all cases with the wide range
in its dcvelopmciit as noted above. R a i d size had n nicaii
length of 25.5, mean width of 4.4, a i d nicaii septa1 attaclinieiit
of 57.9. The mean left aiicl right ventric.ular thicknesses were
25.5 and 11.2 respcctivcly.
Hccf. Tlic inctin btiiicl inetisumiimits were 36.6 in Iciigtli,
9.0 iu width and a septzal nttachniciit of 74.4. The ineaii thickncsscs of t.hc left nnd light rciiti*ic?lox\t'cre 38.0 mid 17.0
respectively.
1)ISCT:ss10A
The conti~aclictory statenients esistiiig in the literature,
as to whether a i~ioclerator loand is pimelit or absent, a r e
due t o differences of opiiiioii aiid iiitci.i”.eiation.
If one Classifies a thickened, but acllicrcnt septa1 trahecula
as a true band (IIoi*and, ’08 a ) , tlicn the structure is always
1,rcscnt. However, several trabeculac are present in the
region of origin of the anterior papillary muscle, when a free
band is absent. lnasmuch as the aiiterior papillary niuscle
lius a partial attachniciit t o the tliiclmied septa1 trabeculac
in such cases (fig. 3 ) , this arrangement is preferably spoken
of as a junctioiial origin of the papillary niuscle (type 2,
Horaricl, ’08 a ) , rather than designating oiie of the ti-abeculae
a s ail adliereiit nioderator band.
E’i~omthe data p i ~ ~ s e n t ein
d table 1, it is evident that tlie
incidence of moderator bands in iiian is soinewhat lower than
the figures of Testut (70 to 805%). It is to be noted that a free
band was present in only 4% of 120 huinwn hearts (type I,
Horund, ’08 a ) while a band entirely free from the scptuni
was found iii 56.Syo of our 500 speciinciis.
Tliesc findings are also contrary to the sta terneiit of Keith
and Flack ( ’06)’ that the c1asSicitll;v dcwribed nioderatoi.
band of the lower ,manimali;iii 1icai.t (slieep) does not csist
in man (see fig. 1).
It is upparciit f r o m table 1 that tllc size of the niocler;itoi*
1)aiitl v a ~ i e swith tlic size and development of the heart in
clifYci.ciit aiiinials. Whether tlie increased band dimensions in
the bee€ lieart, as compared to that of tlie calf, a r e tlue to
liypcrtrophy, or actual increase in cardiac muscle fibers must
awai t further investigation.
Although tlic physiological significance of the imclci’ator
hand is beyond the scope o f the present study, the mean
vcntricnlar thickiiesses of liuirian hearts with and without
lmncls, tlii-om a11 iiitei*cstiiig light upon its assumed function.
Thus if the band plays an active role in preventiug overdilatation of the riglit ventricle during diastole, one mould
c>spcct to find tlic myocardium of the i.iqlit ~ c n l r i c l csoine-
370
R. C . TEUEX A X D L. .T. WARSHAW
what tliicker wlien the band is absent. However, there appears
to be n o significant difference between the iiiean ventricular
thickness in liearts possessing a band, and those where it is
absent.
The moderator b a d wlieii present, is so placed (fig. l),
that it may lend support and leverage to the anterior papillnr)7
muscle and ventricular wall. In addition it has the morphological role of transporting a fascicle of Purkiiije fibers derived from tlie riglit bi*anc*liof tlie a-v hurdle for distribution
to papillary and ventricular musculature.
The custoinary “junctional origin” of the anterior papillary muscle, in the abseiice of a true band, gives this niusclc
a more oblique course and greater leverage. This shift in
papillary position may compensate for the lack of band support, as well a s tlie niiiforni ventricular tliickiiesses i*ecordecl
above.
SUNJIARY
The hearts of 100 cats, 1 2 monkeys, 1 2 clogs, 1 2 sheep, 1 2
pigs, 1 2 calves, 12 beeves, aiid 500 humans wei‘e studied grossly
to determine the incidence a i d size of the moderator band.
A variable pciwiitage (41.6 to 100%) of hands was found
in all the animals, except the dog. Tlie latter animals were
interesting in that there a r c three papillary muscles arising
directly froiii the septum, in addition to the small constaiit
papillary muscle of‘ tlie conus.
The size of tlie moderator band is proportional to the size
and development of the respective liearts studied in this series
of animals.
I n man a true band was present in 56.3g, of the cases, aiid
had the following mean nieasm.ements : 12.7 iiini. in lengtli, 6.0
inm. in width, arid a septa1 attachment of 39.1 11111~.
Measurements of the ventricular thicknesses in human
liearts with and without banchi, did not show any significant
difference.
Tlie moderator bard when pi.esent, appears to lend support
and leverage to the anterior ventricular wall and papillary
muscle. 111 addition this hand ti-ansportsa fascicle of Purkinjc
MODERATOR BAND
3T1
fibers from the right branch of tlic a-v bundle t o the papillary
and ventricular musculature.
When a true nioderator band is absent in nian (43.270),
tlie anterior papillary niuscle arises froiii tlie juiictioii of the
anterior ventricular wall and intermuscular septum. This
shift in papillary position gives tlie niuscle better leverage
a i d a iiiore oblique course. It is suggested that this alteration
may coinpensate for the lack of band support, as well as
explain the above uniform ventricular thicknesses.
LITISRATIrRE C'lTEI)
,\RG\I
D,
R.
I912 Sur la structure de la I3:indrlctte Aiisifoi-inr. Conipt. Itcncl.
1Iebd. Soc. Biol., rol. 72, pp. 152-154.
I ~ R O Wz I ( 1896 Urbcr niiomale Srhnenfkdcn ini Herzeii uiid dcrcn c\ cwtnclle
Eerleutung. Virrhow 's Archir., rol. 145, pi). 649-632.
CROW'N, J I C 1 ) O N \LD
1889 The constrnctioii of t h r rcwtricles in the niamni:r~i:ii~
heart. J. Anat. and Pliys., vol. 23, pi). 250-2553.
IIORAND,R. 1908 a Le faisceau arqu6 ou modcr:itor hand du xcntiiculc droit
dn coenr l'liomnie et drs grands qnadriip&lrs clonie\tiques. Lynn 1116(1.,
rol. cx,pp. 120-127.
1908 h Ile faisce:iu traiisrcrsal dii rocur gauche de 1'homnic. 14von
Nkd., vol. C S , pp. 599-608.
HUCHARD,
IIENRI 1893 Contrihntion 5 1'Ctude cliiiiqnc dcs tendonr; a1wrr;iiits
du roeur. Rev. de nii.d., ~ o l 1. 3 , 1)p. 11:&122.
KEITH, A., AND R f . W. F L S C R 1906 The nuriculo vrntricular bundle of tlic
1iiiin:in heart. Lancet, rol. 2 , pp. 359-364.
KING,T. W. 1837 An essay on the s a f e t y - l a h e fuiictioii in tlie right ventricle
of the human heart, and the gradations of this fnnction iii the
circulation of warin-l)looded animals. Gny 's Hosp. Reports, rol. 2 ,
~ 1 3 . 104-178.
~fO'NcIiBeRG, .T. G. 1908 17rher die sogenaniitcn :tl~norme~iSchneiifaden iin
liiiken rent1 ilrcl des nienschtichen Hemens und ihre Beziehungeii ziiin
Atr ioreiitrikularbiindel. Vc~liaiidl.(1. dentsch. path. Gesellseh., T ol. 12,
pp. 160-165.
R.
1909 The moderator band and i t s relations t o the papillary muscles,
with observations on the drrelopnieiit and stvnctnrc of the right
rentricle. Johns Hopkiiis Hosp. Bull., 1701. 20, pp. 168-176.
ROTT,rsrros, H. n. 1897 IIcxart showing a muscular hand passing betneen thc
t\ro niusciili papillares of the left tcntricle and c:ip:~ble of acting as
n moderator band. J . An:it. and Phys., 701. 31, pp. xxi-xxii.
SPR, M IRC 1874 Sur le nioile de foactionnement des valvules auriculo rentriculaires dn coeur. Arch. d'anst. e t dc pliys., 2eS., \ n l . 1, pp. 532-577,
RXTZER,
848-883.
372
11. C. TRUEX B X D L. J. WARSEI-ISW
T.Iw.%K.\, SVX.\O 1906 Tfas Ecizleitongssj s t e m clrs S:iu~etierlierz~iis. Gust.
Fisher, Jena.
TCSTLT,L. 1905 Traite d’anntoniie hum;tine. Vol. 2 , 1’1). 19-20. Octave Doin,
Paris.
TITRSER,
SIR Wiv. 1893 A human heart with moderator bands in the left
ventricle. J. Anat. and Pliys., x-01. 27, pp. six-sx.
1896 Anothcr heart with moderator bnnd in the left rentricle.
.T. Aii:at. aiid Plrys., 5 01. 20, 1). 368.
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band, incidence, mammal, size, man, moderator
1/--страниц
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