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Note on the behavior of trypan blue injected into the developing egg of the hen.

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Resumen por el autor, George B. Wislocki.
Nota sobre el comportamiento del azul tripan inyectado en el
huevo de gallina en vfas de desarrollo.
Una soluci6n coloidal, el azul tripan, fu6 inyectada bajo precauciones asepticas en huevos durante el und6cimo dia de incubaci6n. El pequefio orificio abierto en la cAscara, a trav6s
del cual se inyect6, fu6 cementado, volviendo a colocar el huevoen la incubadora. Despu6s de dos dias se abri6 el huevo
examinando el embri6n. El colorante fu6 inyectado en la c6mara abrea, sac0 vitelino, sac0 alantoideo, sac0 amni6tico y
en el mesoderm0 del alantoides. En cada una de estas regiones
se comporta de mod0 diferente. La membrana de la cascara
que rodea a la cAmara a6rea le absorbe rApidamente. Escapa
desde el sac0 vitelino a travds de las cklulas epiteliales endod6rmicas que forran el sac0 interiormente, pasando a1 mesodermo subepitelial, donde es absorbido y almacenado por las
c6lulas mononucleares que rodean a un plexo de vasos vitelinos.
Cuando se inyecta en el sac0 alantoideo el colorante no es absorbido. Cuando se inyecta en el sac0 amni6tico tifie alepitelio
amni6tico y tambikn penetra en el tracto gastrointestinal del
feto por la boca. Cuando se inyecta directamente en el mesodermo de la membrana fetal se difunde en la corriente sanguinea del feto tifiendo vitalmente a1 embri6n.
Translation by JoSe F. Nonidez
Cornell Medical College, New York
A C T H O H 3 ABSTRACT OF THIG P h P E R IGSUED
B Y T H E n i n L I o G R . % P i i i c S E R V I C E , OCTOBER
17
KOTE OK THE BEHAVIOR OF TRYPAN BLUE INJECTED
IKTO THE DEVELOPING EGG OF THE HEN
G. B. WISLOCKI
Anatomical Laboratory, Johns Hopkins University
THREE FIGURES
Attempts have been made by several investigators to determine
the fate of dyes injected into the egg and their effect upon the
embryo, but the experiments, though yielding a few results,
were very brief.
Zaretsky ('10) injected trypan blue, trypan red, neutral red,
methylene blue, fluorescin and eosin into developing eggs, and
obtained results of greatest importance with the first trvo. He
injected 0.5 to 1 cc. of one of these dyes into the air chamber of
the egg, and after a period of days noted a slight staining of khe
amniotic fluid, but never any staining of the embryo itself. I n
other instances, after injecting the dye into the outer wall of the
allantois, he observed a faint staining of the entire embryo, fetal
membranes, amniotic fluid, and albumin sac. He stated that
of the tissues of the embryo the kidneys were the most deeply
stained, indicating a rapid excretion of the dye by that channel.
Granules of dye could not be identified microscopically in the
tissues.
Griiper ('la) reported the staining of early chick embryos
with neutral red, trypan blue, and trypan red, but nothing
more than diffuse staining of membranes and embryo alike was
observed.
The most valuable results following the injection of dyes into
the developing chick so far reported are those obtained by
Bakounine ( '95). She injected indigo carmine intravenously
into a series of chicks ranging in age from three to fifteen days;
excretion of the dye by the tubules of the wolffian bodies was
demonstrable in the entire series.
267
268
G . B. WISLOCKI
The present paper is a preliminary account of some observations upon the behavior of trypan blue injected into developing
eggs. The experiments were undertaken in spite of the failure
of previous investigators to make any significant observations
with vital dyes in the chick. It was hoped that by injecting
the dye into different regions of the egg, some knowledge concerning t,he functions of the fetal membranes, and possibly a
successful vit,al staining of the embryo, might be obtained.
Chicks of eleven days’ incubation were used. Trypan blue,
which forms a colloidal sol, was made up in 1 per cent strength
in sterile distilled water. The injections were made with a
syringe bearing a 26-gauge needle, 1 inch in length, through a
nick in the shell, the opening being no larger than necessary to
admit the needle. The trypan blue solution (0.2 cc.) was injected
into each egg, whereupon the needle was withdrawn and the tiny
opening in the egg-shell sealed with a drop of melted paraffin.
The eggs were then returned to t h e incubator to be opened at the
end of forty-eight hours-the thirteenth day of incubation.
By this method, of course, it cannot be determined exactly
at the time of injection into what region of the embryonic membranes the trypan blue has been injected. If, with a general
knowledge of the orientation of the fetal membranes and embryo,
a number of eggs are injected, each locality which it is desired to
inject will be reached in a certain number of eggs. This is made
plain by reference to the diagram shown in figure 1, which
illustrates condit)ions in the egg about the eleventh day. Thus
i t will be seen that by stabbing a needle into the egg, with a
knowledge of the orientation of the structures within, one will
in many instances inject, with precision the yolk sac, allantoic
sac, amniotic sac, etc. Orientation is made easier if one remembers that, after the egg has lain undisturbed in the incubator for
a few hours, theembryo floats to the upper surface; hence the
amniotic sac is more readily injected from above, and the yolksac from the side or below. Suffice it to say that in a series of
five dozen eggs, injected as described above and killed on the
thirteenth day of incubation, all of the selected points have been
successfully injected. X description of the findings in each of the
groups follows.
TRTPAN BLUE INJECTED INTO EGG O F H E N
269
Injection into the air chamber. The air chamber is a cleft
between the two layers of the shell membrane. The membrane
is composed of matted fibers of organic substance which cross
one another in every direction. When trypan blue is injected
into this chamber it is rapidly absorbed by the shell membrane,
much as it would be by blotting paper, staining it a deep blue.
The adjacent structures beneath the shell membrane, namely,
the chorion and allantois, as well as the embryonic fluids, remain
Fig. 1 Schematic representation of a chick approximately on the tenth day
of incubation, showing the technique used in injecting diffcrent localities of the
egg.
unstained and consequently also the embryo itself. When the
shell membrane is removed, the inner surface of the shell is
frequently found colored in the neighborhood of the air chamber.
Injection into the yolk-sac. On injecting trypan blue into the
yolk-sac the dye remains somewhat localized in the yolk in the
neighborhood of the injection, lending a greenish appearance t o
the yolk. The trypan blue, together with the yolk, is absorbed
by the endodermal epithelial cells lining the interior of the
yolk-sac. The dye imparts a greenish-blue coloration to the wall
of the yolk-sac. Microscopically, a greenish, diffuse coloration
270
G . B. WISLOCKI
of the cytoplasm of the yolk-sac epithelium is visible. The
dye enters the epithelium most abundantly in the region of the
area vasculosa, where the mall of the yolk-sac is thrown into
numerous folds covered by large columnar cells which possess
swollen ends and the cytoplasm of which is closely filled with
droplets of yellow substance.
Fig. 2 Photomicrograph of the wall of the yolk-sac of a thirteen-day chick,
showing a portion of the areavasculosa. A group of cellswhich ingest vital dye (a)
is seen adjacent t o a blood vessel. Other groups of cells (b) m e hematopoietic
and do not phagocytize dye.
The dye eventually penetrates the basement membrane upon
which the endoderm rests and reaches its final destination in
groups of cells surrounding the rich venous network in the
yolk-sac wall. These cells are closely associated witJh groups
of hemoblasts which invest the blood-vessels. The former
are round or polygonal and possess a central or slightly
eccentric round nucleus. Their cytoplasm absorbs the vital
dye and stores it in the form of closely packed blue granules
(fig. 2). These cells appear to be the ultimate destination
TRTPAN BLUE INJECTED INTO EGG OF HEN
27 1
of the dye injected into the yolk-sac, as no evidence of its further passage is discoverable. The endothelial cells lining the
blood-vessels remain unstained and, since the embryo itself
does not become vitally stained, it is unlikely that any of the
dye escapes into the vitelline vessels. It is of interest to note
that in spite of the fact that throughout incubation the yolk-sac
possesses a connection through its stalk with the intestine, none
of the dye injected into the sac enters the intestine through this
opening.
Injection into the aZZantoic sac. When trypan blue is injected
into the allantoic sac it mixes uniformly with the allantoic fluid,
coloring the latter dark blue. The dye does not escape from the
allantoic sac-a fact which can be demonstrated in several ways.
If the discolored allantoic fluid is drained off and the sac washed
out with physiological salt solution, the allantoic membrane is
found to be unstained. The fact that the embryo and all its
membranes are unstained confirms the view t,hat no dye has
escaped from the allantoic sac. Furthermore, microscopic
examination of the wall of the sac reveals the absence of the dye
in the delicate, flat polygonal cells which cover its surface, or
in the layer of star-shaped cells just beneath the surface. These
observations accord well with the view that the allantois is
a reservoir for the excretory products of the rnesonephros and
met anephr 0s.
Injection into the amniotic sac. Trypan blue mixes uniformly
ith the amniotic fluid. The amniotic membrane becomes pale
blue due to the presence of dye, which in some instances is
visible under the microscope as blue dust in the delicate, flattened
epithelial cells lining the surface of the membrane. The stomach
and intestines invariably contain dark blue stained mucoid fluid
which indicates that the amniotic fluid is swallowed by the embryo. Stained fluid is also observed in the lumen of the trachea
and primary bronchi. A pale blue staining of the entire embryo
is frequently observed, but the quantity of dye is insufficient to
make it visible in the tissues when examined under the microscope.
272
G. B. WISLOCKI
Injection into the mesoblast of the allantois. When trypan blue
is injected into the mesoblastic tissue uniting the allantois with
the chorion and amnion, vital staining of the embryo results.
This is due, no doubt, to the easy access which the dye has to
the network of allantoic vessels through which it is soon conveyed to all parts of the embryo.
The membranes and integument of the vitally stained embryo present a light blue aspect. The yolk remains unstained,
as does also the shell membrane and the shell itself. The depth
of color in the various organs of the embryo proper varies: the
central nervous system is unstained, the arteries are conspicuously
blue, the lungs pale blue, the liver is greenish blue, the spleen
reddish blue. The wolffian bodies are by far the most deeply
stained organs; the metanephros is appreciably blue.
Microscopic examination of the tissues reveals the presence
of trypan blue in granular form in several of the organs. I n
the thirteen-day-old chick it is found in most abundance in the
wolfian bodies. Here it occurs in the shape of numerous tiny
granules in the epithelium lining the uriniferous tubules (fig. 3).
As might be expected from our knowledge of the distribution of
vital dyes in the adult renal apparatus, no dye is discovered in
the glomerular capsules. In the metanephric tubules, which at
this period are already quite distinct, only traces of the dye are
visible. It would appear, then, that a t this period of development the wolffian body still serves as the main pathway of excretion, though regressive changes in the tubules are already plainly
visible.
The second organ in which trypan blue appears in abundance
is the embryonic liver. The dye is found microscopically in
nearly all the endothelial cells lining the sinusoids and the terminal branches of the portal vein. In the liver cells themselves
no particles are visible.
The spleen, which in the thirteen-day-old chick is a small
round organ approximately 2 mm. in diameter, contains traces
of trypan blue which appear to be within cells lining the vascular
channels and occasionally within mononuclear cells lying free
within the sinuses.
TRYPAN BLUE INJECTED INTO EGG OF HEN
273
Kowhere else in the tissues of the embryo is trypan blue
abundant, although traces of dye are encountered not infrequently in the connective tissue in cells resembling clasmatocytes.
That there are cells in the connective tissue of the chick capable
of phagocytosis is best shown by examining the mesoderm at the
site of injection of tJhetrypan blue into the wall of the allantois.
Fig. 3 Photograph of a drawing of t h e wolffian body of a thirteen-day-old
chick, showing a glomerulus with the bcgiiining of a tubule. The black dots represent granules of vital dye.
Here numerous mononuclear cells, some of them round, others
irregular in outline, are encountered with dye granules within
their cytoplasm.
The behavior of trypan blue in the thirteen-day-old chick
seems to be of sufficient interest to warrant an extension of
these observations to other stages of development. The findings
described suggest paths of investigation which i t bemight of interest to pursue. For instance, an investigation of the function of
the mesonephros and the permanent kidneys as excretory organs
274
G . B. WISLOCKI
during embryonic life would be of considerable value. A study
of the absorption of vital dyes from the yolk-sac at different
stages would likewise furnish us valuable knowledge concerning
the physiology of absorption in the embryo. The method used
in these experiments will, however, never be applicable to chicks
under four or five clays. In thesc younger stages direct observation of the living developing chick under the microscopewill
always prove more satisfactory.
SUMMARY
A series of experiments is described upon the behavior of a
vital dye, trypan blue, injected into the developing egg of the
hen, and the technique of injection is given. In t.he vitalIy
stained chick granules of dye are found in cells of the mesonephros, metanephros, liver and spleen.
REFERENCES CITED
BAKOUNINE,
SOPHIE 1895 Sur l’activit6 sdcr6tice des Bpithhliums de Wolff e t
des Bpithbliums rknaux dans les premiers jours de d6veloppement
embryonnaire. Arch. ital. B i d , val. 23, pp. 350-354.
G R ~ P E RL., 1911 Beobachtung von Wachstumsvorgtingen an Reihenairfnahmcn
Iebender Huhnerembryonen nebst Bemerkungen uber vitale Piirbung.
Arch. f. Entwcklsmech., B. 33, S. 303, 327.
ZARETSKY, S. 1910 Versuche iiber vitale Farbung des Embryo. Virchow’s
Arch. f. path. Anat. u. Physiol., Bd. 207, S. 25-45.
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