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Incomplete posterior duplication of the body (dipygus) in an albino rat.

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The TF’iilur Institute of Aiiatoiiiy and Rzolopy and Dcpnrtrnciit of Putliology, of Prnitsylzunia, Plriladelpliza
The anomalous nialc here reported appeared in the st rain
of inbred albino rats that has been maintained at The Wistar
Institute since 1909. It belonged in a litter, comprising two
males aiid five females, born December 28, 1938. Litter i r i ~ t e s
and tlie forty-seven other ofispriiig of tlie same parents were
normal. Somcwliat smaller than other members of the litter
at birth, this abnormal male grew very slomly during t l ~ c
suclding period, but otherwise seemed healthy and moved actively about the cage until it TVRS about 45 days old. Tlieii
signs of pulmonary suppuration appeared and the abdomen
became so clisteiiclcd by the developmeiit of several firm, irregular masses that locomotion was difficult. As death seemed
imminent, the rat was killed when 56 (lays old. At this time it
had a body weight of 111 gin., the weight of a normal litter
brother being 187 gm.
9 “cloiible monster’’ had never been found previously
iimong the inbred albinos, althougli over 70,000 r a t s liad been
born in tlic strain. It seemed possihle, therefore, that this
unique individual might be a mutant type, not recorded for the
rat, although known to occur in mice where heredity seeniiiig1.iplays an important role in its development (Danforth, ’30).
Wlicii iiiature, normal litter mates of this aiiornalous rat were
inbred, as were a number of their descendants through t h e e
generations. All of the young, approximately 200 individuals,
were nornial. This finding indicates that the malfoi*inationwas
not of geriiiiiial origin, but a sporadic case that can be interpreted, iii accordance with Stockard’s ( ’21) view, as due
to some unfavorable intrauterine condition ~ l i i c l lcaused an
arrest or slowiiig of its developmental rate dnring a particular
period of foetal life.
Head, thorax and anterior extremities of this animal were
perfectly formed. Suspended from the anterior abdominal
Fig. 1 Tenti a1 view showing tlirce liiiidleg~ uiid the inipcrfect forcleg that
deve1oT)ed from thc :ibdoininal wall. The 1ii:iss to tlrr left of tlie mid-line is p:wt
of the fourth hindleg. The bulging lower abdoineii is slioivii.
wall was a narrow, flaccid, tulmlar structu1.c which terminated
in an incompletely dercloped forefoot (fig. 1). The right
hiidleg was about twice normal di;imeter throughout its length
and divided longitudinally just above the ankle into two u11equal halves each of which carried a complete foot. l’he lateral
one of these feet furictioiied as the right foot of the animal,
while the median one, a left foot, w a s fully flexed, curved
slightly towards median line of the pair, and fixed in position.
The functional left liindlcg was eritircly nonnal, but to the
left of the anterior mid-line, loosely joined t o the pubic region,
was a single, complete right hinclleg. This was so placed as
to drag 011 its lateral surface, but could be moved into alniost
Fig. 2 Dorsal view with the Iiiiidlegs :nid tail in the usual l)ositions when
t h e anillla1 was free.
any positioii. Whetlier or riot voluntary rnotioii of this member
TWS possihle is uiiknowii. In a n y event, it appeared wasted
or nridei.-developcd (fig. 2).
Tlie iritcrnal structures of the head, neck, and t11oi.n~were
not unusual except for lobular consolidation of thc
lungs. Likewisc tlie liver, splecii, paii(was, stomach, kidneys aiicl ailiwials lincl developed normally. But, about 4 em.
distal to tlic stomach, a sliort portioii of the small intestine
was moderately expriclecl arid beyond this point the entire
iiitestiiiirl tixct was dnplicatetl. From tlie miicous surface of
tlic intestine, tlie division was less abrupt tliaii iiiclicated by
cxteixal appeal-ances. Iiiteriiallp tlic separation began well
al)ovc tlie point a t wliicli the s e r o ~ ssurfaces divided, and
Fig. 3 Dingraniiliatic sketch of a b d o n ~ i ~ ~: a~ln d 1)rlric viscera. Outlines of
the Iiiiidlrgs ;ind toil parinit orient:ition, 1)ut cwtnin org:ins w e w (1ispl:tced so
th;it aiiatomicnl arrairgeiiients could ~ J Cslio\vn. See teat f o r description. (Appmxiiiiatelg natural size.)
tlie tubes were u i i q u i d , the k f t Iwiiig Iwi*gclrand its ostiuiii
wider (fig. 3 ) .
Tlie left brancli of tlic iiitestiiie connected with R normal
cecum, eoloii aiid amis i n ~vliichthe contents were of the usual
cliaraclei~. Tlie riglit l)imic11of the siiiall intestine also joined
a cecum and eolo11, bnt the cecum and distal half of tlic large
in t es ti11c we rci di stencl(d bv twmpac t etl fecal mass c s ~ 1 1
quantities of irioi*pinic crystalliiie matcirial.
~ 1
The expanded terminal right colon and rectum were densely
adherent to pelvic surfaces at various points and, in the perineal region, had almost perforated into the subcutis. Dense
adhesions also bound the distal end of this segment of the gut
to a larger thick-walled Idadder-like structure which was
placed in the anterior mid-line above the pelvic brim. The
right rectum emptied into the neck of this viscus by a small
circular opening about 1mm. in diameter. The mucosa of this
bladder, of its opening into the rectum and of the rectum was
continuous and intact. The neck of this bladder opened into a
thin-walled tube of irregular diameter, the lumen of which
expanded into three saccular diverticulae, the last just above
the penile urethra, with which the tube was continuous (fig. 3).
Surrounding this irregularly expanded channel were dense
masses of inflammatory tissue. This bladder-like structure
and the sacculated tube contained material similar to that in
the expanded colon.
To the left of the large bladder lay the smaller, normal,
urinary bladder, attached to it by thin, membranous tissue.
Normal ureters, arising in the two normally formed and placed
kidneys, entered the neck at the usual position. Rudimentary seminal vesicles and prostate lay dorsal to the neck of
the normal bladder which continued as a thin-walled tube
(membranous portion of urethra?) t o join the channel leading
to the penis (fig. 3 ) . The penis was in the normal position,
but small, apparently underdeveloped. Bulbourethral glands
were not found.
Placed at the left of the tail’s base a small scrota1 sac
contained a normally formed but small testis, from which the
ductus deferens passed through the inguinal canal to join the
urethra. On the right was found another small testis, placed
in a thin-walled subcutaneous sac on the medial surface of
the doubled right thigh, nearer the knee than the groin. The
duct from this body passed dorsal to the distended right
colon and central bladder to the urethra. The spermatic arteries for this pair of gonads were traced to the aorta (fig. 3).
€I. L. R A T C LI F F E A N D H. D. K I N G
Attached by a short, broad mesentery to the lateral wall of
the distended right large intestine were two spherical
pale, ivory-white bodies 4-5 mm. in diameter and supplied by
blood vessels from tlie wall of the gut. These were taken
to be a second pair of testes.
Opaque material in the blocked half of the intestine and in
the central bladder obscured roentgenograms of the pelvic
bones, and the bones of tlie hindlegs were too complex in their
arrangement to allow suitable views. Therefore details of
Fig. 4 ( A ) Bones froin appendage attached to abdominal wall. (B) Median
aspects of right pair of innominate bones. ( C ) Ventral aspects of pelvic and
adjacent vertebrae. (D) Ventral aspects of lcft pair of innominate bones.
the skelton were studied after the body had been clcareci and
stained under the direction of Dr. E. J. Farris.
Tlie spinal column was not abnormal except for minor variations in the contours of the lateral processes of the vertebral
bodies. The pelvic skeleton consisted of a single sacrum to
which was attached two pairs of innominate bones (fig. 4,
B, C and D). One ileum of each pair seemed fully developed,
and articulated with the sacrum. The right pair of innominate
bones, sketched in figure 4,R, from the median aspect, formed
a sharply angular and abnormally long symphysis, the apex
of which pointed to the mid-line of the animal. I n the riglit
half of this pair the pubic bone was short and heavy,
the ischium moderately distorted and the ilium approximately
normal. I n the left half, lack of development of the ilium
was particularly notable, while other elements were nearly
Acetabula had formed in the usual position, and tlie femora
articulated normally. These were approximately equal in
length, but the median one of the pair measured about half
its fellow's diameter. The bones were not joined, although
closely placed a t the distal ends. However, the tibiae fused a t
the epiphysis and through the upper third of the shafts, but
otherwise had developed completely. The fibulae, on the other
hand, did not, a s is normal for the rat, fuse with the tibiae,
and each was lateral to the companion bone, offering further
proof of the opinion that right and left legs made up this
complex. Bones of the right functional foot of this pair were
complete, but tarsals of the left foot had fused.
Of the left pair of inmominate bones (fig. 4, D) the dorsal
or left half seemed complete, while the right or ventral half
was smaller and tlie ilium distorted into a horn-shaped structure. The symphysis had not fused, although the pubic bones
were joined by a cartilaginous band.
Acetabula also had formed in this side, and bones of
the legs were complete, although those of the median, or
right leg, were delicate and tlie shaft of tlie femur had been
fractured and separated in the proximal third.
The tubular structure that was attached to the anterior abdominal wall contained one narrow, elongate bone, the proximal end of which formed a flattened, subterminal bulb.
Possibly this was a humerus. Articulating with its distal end
was a group of short, thin bones, forming a sort of socket
with it and ending in malformed digits (fig. 4, A ) .
Duplication of parts of the posterior region of the body
has been variously classified. The present case corresponds t o
dipygus of Wilder. ('04), whose material was taken mainly
from congenital deformities of man. Usually doubling of
the posterior extremities is associated with bifurcation or
duplication of the genitalia, the large bowel, and the spine to
or above the lumbar segment (Ballantyne, '04; Wilder, '04;
Schwalbe, '07).
Only three cases of dipygus have been described in rats,
one by Conrow ( '17), one by Altman ( '26) and the present one.
The spine in each of these was single, although deformities
of the hindlegs and internal organs were essentially similar
to those found in analogous forms of monstrous development
described for other species.
ALTNAN,F. 1926 Eiii Fall von Hypogastrius Parasiticus bei einer Ratte (Duplicatus Asymmetras ventralis infraumbiliealis Sehwalbe'). Ztsch. f.
Anat. u. Entwiriekl., vol. 79, pp. 413-432.
J. W. 1904 Antenatal pathology. Wm. Green and Son. Edinburgh.
("ONROW, S. B. 1917 A six-legged rat. Anat. Rec., vol. 12, pp. 365-370.
C. H. 1930 Developmental anomalies in a special strain of mice.
Am. J. Anat., vol. 45, pp. 275-287.
SCHWALBE, E. 1907 Die Morphologie der Missbildungeii des Menschen und
der Tiere, Teil 11, Die Doppelbildungen, Fischer, Jena.
C. R. 1921 Developmental rate and structural expressions: an experimental study of twins, 'double monsters" and single deformities,
and the interaction among embryonic organs during their origin
and development. Am. J. Anat., vol. 28, pp. 115-277.
H. H. 1904 Duplicate twins and double monsters. Am. J. Anat., vol.
3, pp. 387-472.
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albina, posterior, incomplete, body, rat, dipygus, duplication
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