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Studies on amphibian metamorphosis. XIV. Transformation of dermal plicae into tympanic membrane following heteroplastic transplantations

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Department of Biology, University College, New Pork University
The development of the dermal plicae folds in the anuran
constitutes a striking integumentary change during larval
involution. Shortly following the onset of metamorphosis,
the plicae make their appearance, externally, as rather broad
indistinctly outlined stripes of a lighter coloration than the
adjacent integument. Usually two sets of plicae develop, viz :
the dorso-lateral dermal plicae running from the dorso-posterior border of each eye to a point just lateral to the region
of the future urostyle prominence and the lateral dermal
plicae on each side of the upper jaw running from a point
just anterior and ventral to the external nares posterior on a
level just ventral to the future ear region to a point just dorsal to the origin of the fore limb. During metamorphosis the
plicae become increasingly whiter in shade while the integument is thrown into a pronounced ridge. Histologically, the
integumentary folds are characterized by a much thickened
stratum compactum and a greatly enlarged stratum spongiosurn, the latter hypertrophy being due to the concentration
of mucous and poison glands of abnormally large size. The
differentiation of these glands may be said to be completed
by the end of larval involution although further enlargement
occurs during the growth of the young frog.
'The term tympanic membrane or membrane as used here and throughout the
present paper refers only to the integumentary portion of the tympanic membrane and is not meant to include the lamina propria or internal epithelial
The writer ('31) has shown that the areas of larval integument giving rise to dermal plicae structures are specific for
such developments as compared with other body integuments.
I n this work autoplastic transplants of skin from dermal
plicae regions of fully-grown larvae were interchanged with
integumentary grafts from the back, side and belly. During
metamorphosis the integumentary transplants obtained from
dermal plicae regions invariably developed dermal plicae
structures irrespective of their location while, conversely,
integument from the back, side or belly transplanted to the
dermal plicae regions never developed dermal plicae structures. I t was thus concluded that the potentiality for the
development of dermal plicae structures is determined in certain restricted regions of the larval integument at some time
during the growth period of the tadpole. The exact stage
at which this differential potentiality first appears was not
determined, however.
The stability of fully-formed dermal plicae has recently
been tested by the writer ('33). I n this work, dermal plicae
transplants were obtained from young R. palustris frogs and
transplanted to non-metamorphosing R. palustris and R. catesbeiana larvae. Histological examination 3 weeks following
such transplantations showed that the homoplastic transplants had maintained their initial dermal-plicae structures
although growth of component parts was not apparent. I n
direct contrast to this finding the heteroplastic transplants,
during the same time interval, were found to have undergone
considerable regression resulting in the complete disappearance of all structural features differentiating dermal plicae
from ordinary body integument. Apparently, therefore, influences necessary f o r the maintenance of developed dermal
plicae structures were lacking in the R. catesbeiana larvae
although present in the R. palustris tadpoles.
The results of the above described work suggested several
correlated problems of interest to the writer. The fact that
total regression of dermal-plicae structures can be obtained
following heteroplastic transplantation raises the question of
whether o r not the potentiality for dermal plicae formation
is also lost or whether it is retained. If the latter is true,
then the possibility of re-developing dermal plicae structures
in the same integument following suitable retransplantation,
suggests itself. A second and even more interesting possibility exists in that such integument having undergone total regression of dermal plicae structures might be capable, following suitable retransplantation, of developing an entirely
different set of histological structures such as is characteristic of the integumentary portion of the tympanic membrane.
The present paper describes the results of experiments designed to test out the two developmental possibilities described
Regression. of dermal plicae f ol1oauin.g heteroplastic
transpl ant at ion.
The dermal plicae integument used in the first transplantations was obtained from young R. palustris frogs collected
during the latter part of June and early part of July, 1933,
in the vicinity of Lake Winnisquam, New Hampshire. The
specimens utilized had attained but little growth, having completed metamorphosis but 2 to 3 weeks previous. The dermal
plicae folds, however, were well developed, being sharply defined and white in appearance externally. This was especially
true of the dorso-lateral dermal plicae.
The transplantation procedure was, briefly, as follows : A
rectangular piece of integument was cut (fig. 10) a little posterior to the eye so as to include a portion of the dorso-lateral
dermal plicae fold and a small amount of the adjoining back
integument. This integument was now removed and transplanted to the back of a R. catesbeiana tadpole, the transplantation site having first been prepared by the removal of
a. similar sized rectangle of back integument. I t was essential
for the purpose of the experiment that the host animals would
not undergo metamorphosis for a t least 2 months. Actually,
the larvae used were second year forms which normally would
not metamorphose until the following summer. Following
dermal plicae transplantation, the host animals were isolated
in separate bowls and observed daily thereafter for external
signs of dermal plicae regression.
Usually, in about 2 weeks following transplantation, the
dermal plicae as viewed externally were seen to undergo ;I
slight darkening in coloration while diminution in the height
of the fold was also apparent. These two external signs of
histological regression gradually increased until all color
characteristics of the stripe were lost and the transplant as
a whole became quite dark in pigmentation (fig. ll), while
all signs of the ridge or fold were lost. This stage was usually
attained within 5 to 6 weeks following transplantation. Histologically, a definite sequence of degenerative changes accompanied the external signs of regression. The original
transplant (fig. 1)was characterized by a relatively thick epidermis with flattened cuticle cells and from between four and
five layers of cuboidal cells. The innermost layer (malpighian
layer) appeared to consist of the same type of cells as regards
size and shape characteristic of the upper layers. The stratum spongiosum was greatly thickened to accommodate the
abnormally large poison and mucous glands typical of dorsolateral dermal plicae. The stratum compactum was likewise
quite thick and appeared to be divided into two fairly distinct
regions, viz. : an outer more loosely constructed zone in which
the component fibers although assuming a slight wavy formation were never thrown into convolutions, and an inner zone
consisting of very compact bundles of fibers distinctly and
sharply convoluted. The subcutaneous connective tissue beneath, although subject to considerable variation, was usually
quite thick and included blood capillaries, assorted fibers and
Sections made of transplants 2 to 3 weeks following transplantation invariably gave evidence of decided regressive
changes (fig. 2). Although the epidermal cells appeared t o
be larger in size and more columnar in shape, the chief
changes were concerned with the cutaneous glands and the
stratum compacturn. The former were clearly undergoing
rapid degeneration as evidenced by their comparatively small
size and in many cases the absence of all secreting epithelium.
Degenerative substances were frequently found still filling
the lumen at a time when all secreting cells had been destroyed. Phagocytic lymphocytes were also very abundant.
The appearance of the stratum compactum was equally as
striking. Here, the outer zone was in process of rapid dissociation with numerous lymphocytes filling the spaces between the loosely joined bundles of fibers. The lower zone
of this layer, however, was seldom affected t o any marked
degree and usually preserved its compact, convoluted appearance, although sparingly invaded by lymphocytes. The subcutaneous connective tissue was of uniform thickness and
contained nmerous lymphocytes.
Within 5 to 6 weeks following transplantation, all remnants of cutaneous glands had been removed and lymphocyte
infiltration was consequently much reduced in amount (fig.
3). The upper stratum compactum zone was also largely
absent, although individual fibrous elements originally derived from this layer tended to invade the stratum spongiosum area. The lower stratum compactum layer was still
intact while the subcutaneous connective tissue had increased
somewhat in thickness. The epidermis was still practically
normal in appearance with the exception of the malpighian
layer, the cells of which had hypertrophied slightly and assumed a more columnar shape. I n general, however, the
transplant resembled quite closely the structure of normal
integument barring the absence of small cutaneous glands
which are usually found rather uniformly distributed throughout the latter.
One hundred and forty-two heteroplastic dermal plicae
transplantations were made as previously described. Of
these, but forty-one cases survived the 5 to 6 weeks’ period
essential for complete regression of dermal plicae structure.
2 T h e high mortality was undoubtedly due to the effect of the successive heat
waves experienced during the summer of 1933, since mortality of a like degree
occurred among the stock R. catesbeiana larvae.
Thirty-six of these transplants were at this time retransplanted to determine the possibility of redevelopment of
dermal plicae structure or of tympanic membrane formation.
The other five transplants were allowed to remain on the host
animals to determine their subsequent fate. These five transplants were fixed and sectioned at successively later periods
and gave evidence of pronounced histolytic destruction.
Figure 4,for example, represents the condition of one of these
transplants removed after approximately 8 weeks on the host.
It will be noted that the lower zone of the stratum compactum
has finally undergone dissociation and is being rapidly removed by the phagocytes. The epidermal cells of the malpighian layer are greatly hypertrophied and shortly after
this stage undergo histolysis, resulting finally, in the destruction of the entire epidermis which is apparently the last region of the transplant to degenerate.
Heteroplastic retransplantation t o metamorphosing larvae
The retransplantation of integument following complete
regression of dermal plicae structures was undertaken in a n
attempt to redevelop the original structural features as found
in young R. palustris frogs. Logically, such retransplantation should be made to larvae just prior to or in early stages
of involution, in order that the metamorphic influences responsible for dermal plicae differentiation would be available.
Furthermore, since the integument concerned was originally
obtained from R. palustris frogs, retransplantation to larvae
of the same species would have been preferable, assuming
that the 5 to 6 weeks’ period on the R. catesbeiana hosts had
not seriously affected the specific dermal plicae potentialities
of the R. palustris integument. Unfortunately, however, R.
palustris larvae were not available at this time since metamorphosis had been completed fully 7 o r 8 weeks before.
Larvae of R. catesbeiana and R. clamitans were available,
however, and the latter were chosen to act as hosts for the
retransplants. This selection was made on the basis that R.
clamitans larvae normally develop dorso-lateral dermal plicae
while R. catesbeiana larvae do not, although the young frog
of the latter species do possess the lateral or jaw dermal
Nine of the available thirty-six transplants were used for
this second transplantation. I n removing the tissue to be
transplanted, only approximately two-thirds of the transplant
was utilized, the remaining one-third being fixed along with
the entire larvae f o r subsequent histological study in order
to determine the exact structure of the tissue at this time. The
square-shaped piece of integument was then transplanted
either to the back or potential dorso-lateral dermal plicae
regions of large second-year R. clamitans larvae in early
stages of involution. Five retransplantations were thus made
to the dermal’plicae region and four to the mid-dorsal region
of the back. The transplants were subsequently examined
for possible external and histological signs indicative of
dermal plicae formation.
The host larvae underwent a normal metamorphosis, which
process was completed within 2 weeks. Four of the newly
metamorphosed frogs died within 2 weeks following complete
involution while the remaining five lived from 2 to 3 weeks
longer. Thus all nine transplants were subjected t o host influences through metamorphosis, while five of these remained
on the young frogs for from 4 t o 5 weeks. Of the latter, three
had been transplanted to the dermal plicae region and two
to the back.
I n no case were external signs of dermal plicae developed
in the transplants. This was particularly evident in those
individuals where transplantation had been made to the dermal plicae region. Here the normal dorso-lateral dermal
plicae of the hosts became well differentiated as distinct whitish or somewhat pink iridescent stripes as viewed under a dissecting microscope. These dermal plicae stripes developed
directly adjacent to the anterior and posterior borders of the
transplant, but never invaded the latter tissue. The transplants, irrespective of their position, retained the uniform,
darkly pigmented appearance typical of their condition when
removed from the R. catesbeiana hosts. Histological examination revealed the development (figs. 5 and 6) of small
cutaneous glands usually of the mucous type, while partial
reformation of the upper zone of the stratum compactum
layer was apparent. The degree of glandular development
was never such, however, as to definitely characterize the
integument as ' developing dermal plicae, ' since glandular
distribution of this type is quite characteristic of normal
back integument. Perhaps the most apparent change concerned the epidermis which had been reduced from a four to
five layered structure to one consisting of a cuticular layer
and but one inner layer of cuboidal cells. The histological
findings as described above applied equally as well to the back
transplants as they did t o those in the dermal plicae region.
I n general it may be said that the transplants tended to resemble normal integument, with the exception of the epidermis which had evidently undergone considerable histolysis.
Retransplantation to the ear region of metamorphosing
The writer ('28) had previously shown that the integumentary portion of anuran tympanic membrane is formed
from integument in contact with the developing annular tympanic cartilage. That other larval integuments possess the
same developmental potentialities was shown by the transplantation of back and side integument over the annular
tympanic cartilage, resulting in membrane formation in such
transplants during metamorphosis. Conversely, potential
tympanic membrane integument of the ear region transplanted to the back never transformed into membrane structure during larval involution, while transplantation of the
annular tympanic cartilage beneath back and side integument
always induced membrane formation in these tissues. The
dependence of tympanic membrane formation on influences
arising from the developing annular tympanic cartilage was
thus clearly established.
Whether or not integument following complete regression
of fully differentiated dermal plicae structures possesses the
potentiality for tympanic membrane formation in common
with larval integuments, was determined by means of suitable retransplantations. Approximately two-thirds of a
transplant (fig. 11)was removed and retransplanted over the
developing annular tympanic cartilage of a R. clamitans or
R. catesbeiana larva. These second hosts were in late stages
of metamorphosis, at which time membrane formation is initiated. I n making the retransplantation, a square of integument was first removed from the ear region of the host animal
so as to expose the entire ring of annular tympanic cartilage
beneath. The transplant was then fitted to this wound area
so that the entire ring of cartilage was brought in contact with
the integumentary graft. I n all such retransplantations the
remaining one-third of the transplant was fixed ‘in situ’ along
with the first R. catesbeiana host larva for future determination of the exact histological condition prevailing at the time
the retransplantation was made.
Of the twenty-seven transplants available, eighteen were
retransplanted to R. catesbeiana larvae and nine to R. clamitans larvae. While all host animals survived metamorphosis,
but seventeen lived f o r from 4 to 6 weeks following complete
involution. This interval was thought sufficiently long enough
to test the developmental potentiality of the transplants in
question, since, counting the involution period, the latter had
maintained intimate contact with the annular tympanic cartilage f o r from 5 to 7 weeks.
All transplants in contact with the annular tympanic cartilage for at least 2 weeks exhibited external signs of tympanic
membrane formation. These consisted first of a light shaded
area as distinguished from the darkly pigmented transplant
integument and later by the ‘outlining’ of the definitive membrane region, both characteristic of normal membrane formation. With further development, the outlined circular area
became progressively more pale in shade and eventually assumed a light-brown coloration. By this time indentation
of the membrane area as a whole had occurred and the area
had assumed the characteristic macroscopic texture typical
of well-developed tympanic membrane integument. These
latter external changes, however, were not usually developed
until the transplants had been on the host animals for at least
3 to 4 weeks. Due to the shifting of the developing annular
tympanic cartilage, it is rather difficult to so orient the transplant initially, so that the membrane when formed will be included entirely within the boundaries of the transplant.
Usually, therefore, part of the membrane was developed from
transplant integument and the balance from adjacent host
skin. Several cases were obtained, however, in both R. catesbeiana and R. clamitans, in which the membrane developed
practically in the center of the square transplant. Figure 12
represents such a development on a R. clamitans host. As will
be noted, it is frequently possible to detect the location of the
columella beneath, which has by this time established contact
with the lamina propria portion of the membrane. It is of
interest to note here, also, that those portions of the transplant not utilized in membrane formation, maintain the same
macroscopic appearance they had when originally retransplanted.
The final and best criterion f o r the determination of tympanic membrane development is to be found in the histological picture presented. All partial and complete membranes
were sectioned and the degree of cellular transformation
found to be closely correlated with the external changes that
had occurred. I n this respect, it may be said that all stages
in development were found from the initial changes concerning the stratum compactum to the reestablishment of the
stratum spongiosum near the end of membrane formation.
The various histological developments occurred in the same
sequence as previously described in detail by the writer ('28)
f o r membrane formation in R. pipiens.
The most complete and typical transformations were found
in those transplants in contact with the annular tympanic
cartilage for the longest period of time. Figure 9 represents
a cross section through one of these membranes including
associated structures of the ear region, together with the
lamina propia and internal epithelial portions of the tympanic membrane. An enlarged view of the integumentary
portion of the membrane is seen in figure 8. Of chief interest
here is the thin epidermis composed of relatively large cells,
the thin stratum spongiosum usually devoid of cutaneous
glands, and especially the stratum compactum layer which has
undergone a decided transformation. Regarding the latter
layer, the individual horizontal fibers do not appear t o be
grouped together in bundle formation while the wavy, convoluted appearance typical of normal integument is absent.
Nuclei are rarely seen while separation into an upper and
lower zone is no longer characteristic. The layer as a whole
appears t o contain numerous finely dispersed granules which
stain deeply with Heidenhain's hematoxylin. Frequently,
although not always, the cut ends of a second set of fibers
may be seen in the upper region of this layer. According to
Tokura ('25) these consist of small fibers running vertically,
which cross with the horizontal fibers of the inner region to
form a complex network. This condition described by the
writer ( '28) for R. pipiens is apparently also typical of both
R. clamitans and R. catesbeiana tympanic membrane. The
relationship of the integumentary portion of the membrane
t,o the underlying lamina propia was likewise normal in all
respects being sometimes separated by thin subcutaneous
connective tissue in certain regions while in others it was
directly adjacent to the latter layer. I n general it may be
said that membrane development in the transplanted integument on the right side of the young frog was as fully advanced
as that of the normal membrane on the left side of the same
individual. I n order to visualize the degree of transformation undergone by the original dermal plicae integument, a
comparison of figures 1, 3, and 8 is suggested.
The cause of dermal plicae regression following heteroplastic transplantation is of interest t o consider at this time.
Since influences present during larval involution are essential
for the normal differentiation of specific dermal plicae structures, it is possible that the lack of such influences in the nonmetamorphosing host larvae may account for the degenerative
changes which occur. The writer ('33), however, has shown
that regression of fully developed R. palustris dermal plicae
does not occur when the latter is transplanted to non-metamorphosing larvae of the same species. It should be noted,
however, that while differentiated structures are maintained
following such homoplastic transplantation, growth of the
various component parts never occurs as is true of the dermal
plicae elements during the growth of the young frog. The
regression occurring following heteroplastic transplantation
is therefore more probably due to species differences between
host and transplant. This explanation is strengthened by the
fact that continued presence of the transplant on the host
ultimately results in the complete degeneration of the former.
It should be noted, however, that the first structures of the
transplant to undergo regression are the cutaneous glands
and not the epidermal or stratum compactum portions. This
would appear logical since the former constitute the most
highly-diff erentiated structures of dermal plicae integument.
The failure of the R. palustris transplants, following, dermal plicae regression, to develop dermal plicae structures
when retransplanted to R. clamitans larvae is difficult to explain under the conditions of the experiment. Several possibilities present themselves, however. It might be assumed
that the potentiality for such development had been lost due
to the pronounced degenerative changes occurring while on
the first host larvae. This would seem to apply especially to
the redevelopment of large cutaneous glands. The latter normally arise from cells of the malpighian layer of the epidermis
which, during transplant regression, are markedly changed
in shape and size indicative of early degenerative changes.
Hence it is possible that, although they subsequently are able
to give rise to small glandular structures typical of integument in general, they are not capable of deriving the abnormally large type of glands typical of dermal plicae. It is also
altogether possible that species differences may have been
responsible f o r the lack of development. As has been stated
before, it is unfortunate that R. palustris larvae were not
available at the time. A still further possibility exists in that
the developmental influences present in the metamorphosing
Ii. clamitans larvae may not have been as intense as compared
with similar influences present in involuting R. palustris
larvae to which the structural differentiations of the integument in question normally respond. I n this respect it may be
noted that normal dermal plicae formation in R. clamitans
occupies approximately twice as long a period of time as is
true of normal R. palustris dermal plicae development.
The results of the present paper are clear in that R. palustris integument, following complete regression of dermal
plicae structures, is still capable of transforming into tympanic membrane when retransplanted to the ear regions of
either R. catesbeiana or R. clamitans metamorposing larvae.
The potentiality of integument to transform into tympanic
membrane when in contact with the developing annular tpmpanic cartilage is one apparently shared by all larval integument, regardless of its origin (Helff, '28) and such totipotency
is apparently not destroyed by either dermal plicae development or regression in integument. It, is of interest, furthermore, to note that the degenerative changes typical of early
stages of normal tympanic membrane dedifferentiation rescmble quite closely the changes prevalent during dermal
rlicae regression. Hence, it follows that some of the early
degenerative changes necessary for tympanic membrane formation were probably already accomplished before transplantation over the annular tympanic cartilage was carried out.
The later and more profound tympanic membrane developments involving particularly the complete reorganization of
the stratum compactum, were beyond doubt due solely to
influences arising in the annular tympanic cartilage.
The results, in general, emphasize the developmental plasticity of amphibian integument. They also suggest that certain other adult organs and tissues may be directly dependent
for the maintenance of their differentiated component parts
on hormonal, chemical, or other influences constantly supplied
by the animal as a whole. I n other words, the fully differentiated structure may not be unchangeably ‘set’ or ‘fixed’
in that removal of the sustaining influences may lead to reregression and the attainment of a more primitive (embryonic) type of tissue capable in some cases of redeveloping into
an entirely different structure under the influence of other
developmental influences. This concept, coupled with the results of the present paper, has suggested many interesting
possibilities involving structural transformations. The writer
hopes to continue in this field of research as soon as suitable
live material is available.
Integumentary grafts including fully differentiated dermal
plicae structures were obtained from R. palustris frogs 2 to
3 weeks following larval involution and transplanted to the
backs of non-metamorphosing R. catesbeiana larvae. Within
5 to 6 weeks complete macroscopic and histological regression
of dermal plicae structures had occurred. The grafts were
then retransplanted with the following results :
Grafts retransplanted to the backs and to the dermal plicae
regions of metamorphosing R. clamitans larvae showed slight
glandular development within 6 to 7 weeks, indicative perhaps of early dermal plicae formation. Typical fully differentiated dermal plicae structure was never obtained, the
transplants usually tending to resemble normal integument.
Grafts retransplanted to the ear regions of metamorphosing R. clamitans and R. catesbeiana larvae developed into
fully diffentiated tympanic membranes within 5 to 7 weeks.
It has thus been shown that transformation of a fully differentiated structure (dermal plicae) into an entirely different
tissue (tympanic membrane) is possible, following suitable
double heteroplastic transplantation.
0. M. 1928 Studies on amphibian metamorphosis. 111. The influence
of the annular tympanic cartilage on the formation of the tympanic
membrane. Physiol. Zool., vol. 1, pp. 463-495.
1931 Studies on amphibian metamorphosis. IX. Integumentary
specificity and dermal plicae formation in the anuran, Rana pipiens.
Biol. Bull., vol. 60, pp. 11-22.
1933 Studies on amphibian metamorphosis. XI. Development and
regression of dermal plicae following homoplastic and heteroplastic
transplantation. Biol. Bull., vol. 65, pp. 304-316.
R. 1925 iiber den Bau des Trommelfells beim Frosch. Folia Anatomiea Japonica, vol. 3, pp. 165-172.
1 h’ormal Rana palustris dorso-lateral dermal plicae integument from a young
frog as used f o r the first transplantations. Note the thickened epidermal and
stratum compactum layer and t h e large rutaneous glands.
2 Showing partial regression of dermal plicae structures 3 weeks following
transplantation t o R. catesbeiana larva. Note degenerating cutaneous glands and
dissociation of upper zone of stratum compactum.
3 Complete regression of dermal plicae structures 5 weeks following transplantation to R. catesbeiana larva. h’ote absence of cutaneous glands and reduetion of the stratum compactum.
4 Condition of transplant 8 weeks following transplantation t o R. catesbeiana
larva. Note complete dissociation of stratum compactum and hypertrophy of
nialpighian epidermal cells.
RV, blood capillary
P, pigment cell
D , duct of mucous gland
DG, degenerating gland
E , epidermis
M G , mucous gland
PG, poison gland
SB, subcutaneous connective tissue
SC, stratum compactum
SS, stratum spongiosum
0. Y. HEI.FC
ICECOHI>, VOI.. 59. NO. 2
A 1Iixtologic:il :ippcnr:iiieib of H. palustris integui1iwt:iry tr:inspl:int as shown
in figure 3, (i wceks following rctransl)lriitntioii to tlic tlorso-l:itcr:il denii:il plicac
rcgion of r iiic1t:iriiorl)lioxin~It. clriiiitririv 1:irva. X0t.c thin cl!iclrriiiis ant1 sninll
.cutniicous glnnds tlcvc!lopctl niitl gcncr:il tliiekening of xtruturii cmipictuin.
(i Suiiic history as for t.r:iiixpl:iiit illustrritirl in figure 5 , vxcqt rc~trniispltiiitation ni:itlc t.o the buck. Tlic siiiiic histological tlew1opiniwt.s prevail.
i Aplwnrniwe of ~iorai:iI It. eluiiiitriiis intcguiticnt :icl.ineiW to t h i n tyiiluiiiic
8 Showing dctni1c.d strudurc of tynipunic iiicml)rnne as clcrcloped in a traiixpl:mt 6 wccks aftor rctrans~~l:rnt.:itionowr tlic niinuler tyiiipunic c:irtilage of ti
H. rlninitnnr 1:irv:i. The t~xtc~rn:ilnppearance of this int.inl)rnnc
is sliown i n figurc! I?.
SH. subcutniicous conneetire tissue
SC, stratum coiiipactuni
RF, blood capillary
B, cpidcrniis
L, lymphocyte
MC, mucous gland
SS, stratum spongiosuiii
FF, rerticul fibers
P, pignicnt ccll
0. Y. HEI.FC
('rims scv6oii tlirougli thc iiiiddle car region of n youiig It.. el:iiiiitans frog.
Tliv 1:iiiiiii:i 1iropri:i :ind iiiiicr cpithciiiil portions of tlic tynip:iiiic iii(milir:iiic linrc
I w n clcwlolnvl f roiii tlic host, wliilv the intguiiicntnry port ioii of tlic mtwibrniii~
has 1)ccw foriiicvl froiii :I It.. p~ilustristriiiisplriiit ns slio~viiin figurc 3, wtr:insplanted 6 weeks bcforc over t.lie aniiulrir tympanic cnrtilngc. The iiincrolleopic
nppctirniit.e of tho iiicnil)r:inc is illustrutcel i n figure 12.
1.0 Nwroecopic appsirancc of a dorso-latcral cleriiinl p1ic:ic fold i i i n yung
R. pnlustris frog 2 to 3 wccka nftcr conipletc 1:trval involution. Tlic nutiinid
rrctaiigle iiidientes the rrcn of iiitcgniiicnt reniorcd for lictcroplastic tmiisplniiiation.
11 N:acroxcopic :ip~w:ir;iiicc of c1eriii:rl plicw trnnsp1:iiit as xlioivn in figure 10,
5 weeks aftcr transplantation to tlic back of a lion-iiicttiiiiorpliosiug R. cntcsbcinna
Irirvii. 'I'hc! hiatologienl :rppenrr:riicc n t this tiinc is sIio\~nin figure 3 .
I!! Extcrnnl nppcnraiicc of t.yinp:inic incmbrniir in n R.. pulustris tlcriiinl plicac
t.r:iiispl:iiit (i wcvks following its retraiisplnntatiun over tlic riiiiiulitr tyiiipnnic
crrtilngc of :i mct:iiiiorpliosing R..eliiiiiitans larva.
ATC, annular tympanic crrt.ilagc
BV, blood capillary
C, t.ip of coluinelltr
R, epideriiiis
El*', thickcncd elnst.ic filwr rrgion of
lamina propria
I E . inner epithclial laycr of nicml)raiie
12, luiiiiiia propria
M C , mucous gland
P, pigiiicnt cell
SC, strntuni coriipactum
SS. stratuin sponginsuni
TC, tympanic cavity
1'2'. tcnsor tympani
0. Y. HEI.FC
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metamorphosis, xiv, transformation, heteroplastic, amphibia, following, membranes, tympani, plicae, studies, dermal, transplantation
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