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The embryological development of Jacobson's organ in Didelphys virginiana (Kerr).

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Department of Biology, Rosemont College, Rosemont, Pennsylvania
The observations reported in this paper were made as part of a
program to complete information concerning Didelphys virginiana,
undertaken by the Zoology Department of the University of Pennsylvania and The TiTristar Institute of Anatomy and Biology. The author
wishes to express her gratitude to The Wistar Institute for permission
to study its sets of slides, also to Dr. John McClain of Villanova College, and to Dr. Olin E. Nelsen for specimens of various ages for dissection.
The vomeronasal organ of Jacobson lies on either side of the nasal
septum, supported by curved plates of cartilage. This structure was
described and figured as early as 1703 by Ruysch; however, it bears the
name of Jacobson who described it in mammals in 1811.
Many descriptions of Jacobson’s organ in the marsupials have been
written from the standpoint of comparative antomy. There are a few
brief notes on its embryogeny in the opossum, mentioning only “that
it is formed by the invagination of the epithelium into the septum’’
The purpose of this brief paper is to describe the embryogeny and
later development of Jacobson’s organ in Didelphys virginiana.
The numbered stages mentioned below correspond to those used by
McCrady in “The Embryology of the Opossum.”
Stage 30 - is distinguished by the appearance of the oro-nasal groove.
Stage 31 - The oro-nasal groove is converted into a tube. The frontal
process has developed. Median and lateral nasal processes
have grown forward and are fusing with the maxillary
process to form the beginning of the snout. (McCrady.)
Stage 32-One can distinguish the cartilage of the nasal septum. A
shallow indentation of the epithelial lining of the nasal
cavity, on the antero-lateral surface of the nasal septum
marks the anlage of Jacobson’s organ.
Stage 33 - 34. The invagination becomes deeper and forms a diverticulum in the septum. Attached to the blind end of the
sac one finds solid strands of tissue which stain deeply.
Jacobson’s cartilage, or the cartilage of the vomero-nasal
organ appears at this time as a bar anterior to the invaginating tissue. A small blood vessel lying parallel to the
nasal septum becomes associated with Jacobson’s organ.
Stage 35 - The diverticulum elongates. The lumen of its anterior
portion enlarges and becomes crescentic, while its opening
towards the nasal passage narrows. The epithelial lining of
the mesial wall of the sac begins to differentiate into
columnar epithelium.
Birth occurs at the end of stage 35. Pouch young series have not been
given stage names but are usually designated by crown-rump measurements. These were found to vary greatly from litter to litter, hence
actual ages of the young will be indicated here.
One and one-half-day pouch young. Jacobson’s organ is still a simple
diverticulum. The epithelium of the mesial wall of the sac becomes
high columnar epithelium. The cells along the lateral walls remain low,
cuboid epithelium.
Jacobson’s cartilage has become better developed, with the bars
curving inward towards the nasal cavity. Eventually these curved bars
completely encircle the anterior position of Jacobson’s organ, forming
a cartilaginous cylinder named Jacobson’s capsule.
Two-day-old pouch young. No difference from previous stage,
Seven-day pouch yozing. At the cephalic end of the diverticulum the
deeply staining solid strands of tissue seen in stage 34 have hollowed
out to form one or two simple tubes lined with low epithelium. The
opening of Jacobson’s organ into the nasal cavity becomes narrowed
by the development of the palatine processes. Eventually its opening
comes to lie at the nasal end of Stenson’s duct.
S e v e n t o 15-day-old pouch young. These stages show the maximum
development of Jacobson’s organ. Its lumen becomes much enlarged
and bean-shaped. At its cephalic end it communicates with several
tubes whose development was marked in the previous stage. These
simple tubes have become much elongated and branched at the cephalic
end, forming a group of glands known as Jacobson’s glands. Branches
of the olfactory nerve pass through the cribriform plate and end either
in Jacobson’s glands or in the high columnar epithelium of the mesial
surface of the organ. The expansion of Jacobson’s organ, together wit11
the flaring of the supporting cartilaginous bars, produce a marked
protuberance on the anterior portion of the nasal septum (figs. 1and‘2).
As the palatine processes fuse under the nasal septum, the openings of
Jacobson’s organ on each side become further narrowed, or even totally closed. I n some groups of animals Jacobson’s organ opens directly into the nasal or oral cavity. I n Didelphys, however, Jacobson’s
organ opens into the cephalic end of Stenson’s duct which forms the
Fig. 1 Fifteen-day-old pouch young.
( A ) Cartilage of nasal septum.
(B) Jacobson’s organ.
(C) Cartilage of Jacobson’s organ.
(D) Branch of the olfactory nerve.
(E) Duct leading to numerous glands.
( F ) Glands of Jacobson’s organ.
upper part of the incisive canal on each side, opening into the oral
cavity in the vicinity of the median papilla.
A IOg-day-oZd opossum. I n this specimen Jacobson’s organ is a large
flat tube supplied at its cephalic end with numerous glands. It lies in a
cylinder of cartilage lateral to the nasal septum on the floor of the
nasal cavity. Its opening into Stenson’s duct may be completely closed.
Much of the voluminous literature on Jacobson’s organ is concerned
with its evolutionary significance, or with the probable use of a structuke which is accessory to the nose. One of the most striking things
about this organ is its essential similarity in all the groups in which it
appears. “In all, Jacobson’s organ is alike - a tube lined with sensory
epithelium lying in the rostra1 oral end of the septum nasi. Because it
Fig. 2 Fifteen-day-old pouch young. Labels as in figure 1.
( G ) Stenson’s duct, or the naso-palatine canal.
Note in these figures the protuberance on the wall of the nasal septum caused by the enlargement of Jacobson’s organ, and by the flaring of Jacobson’s cartilage.
is associated constantly with the vomer bone it has been called the
vomero-nasal organ. It is associated with glands (Jacobson’s glands)
and is fed from above by branches of the olfactory nerve which enter
the sensory epithelium. It opens either into Stenson’s duct or into the
floor of the nasal cavity, either above, o r below, but always near Stenson’s duct. ” (Mihalkovics.)
1. Jacobson’s organ arises as an invagination of epithelium into
the nasal septum in stage 32.
2. The diverticulum thus formed continues cephalad, becomes associated with a series of tubes and glands. Cartilaginous bars surround
it anteriorly. Branches of the olfactory nerve end in it.
3. The highest development of this organ is reached in 15-day-old
pouch young.
4. In later stages it comes to lie in the nasal septum connected anteriorly to Stenson’s duct which opens by way of the incisive canal into
the mouth cavity.
BAWDEN,H. HEATH 1901 Bibliography of the literature on the organ and sense of smell.
J. Comp. Neur., vol. 2, pp. i-xl.
1920 Das organon vomeronasal Jacobsoni, ein Wassergeruchsorgan. Anat.
Hefte, vol. 58, pp. 137-191.
BROOM,R. 1895 On the organ of Jacobson in monotremata. J. Anat. and Physiol., vol. 30,
pp. 70-80.
R. 1882 Note on the organ of.Jacobson. Quart. J. Micros. Science; vol. 1882, pp.
MCCRADY,EDWARD,JR. 1938 The Embryology of the Opossum. American Anatomical
Memoirs no. 16. The Wistar Institute of Anatomy and Biology, Philadelphia, Pa.
VICTORVON 1898 Nasenhohle und Jacobsonsehes Organ. Anat. Hefte, Bd. 11,
8. 1-107.
ROSE, C. 1893 o b e r das Jaeobson’sehe Organ von Wombat und Opossum. Anat. Anz. Bd.
8, S. 766-768.
SMITE,G. ELLIOT1895 Jacobson’s organ and the olfactory bulb in Ornithorhynchus. Anat.
Am., Bd. 11, S. 161-167.
J. 1891 On the organ of Jacobson in the kangeroo and the rock Wallaby. J.
Anat. and Physiol., vol. 26, pp. 371-374.
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development, virginia, didelphys, jacobson, embryological, organy, kerr
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