ANATOMICAL STUDIES ON THE CELL COLUMNLOCATED CLOSELY MEDIAL TO THE NUCLEUS OF
THE SPINAL ROOT OF THE TRIGEMINAL NERVE
IN THE SPERM AND THE PYGMY SPERM WHALESYASUSHI SEKI
Department qf Anatonry, Kanazawa Medical University, Ishikawa

ABSTRACTA specific cell column was examined anatomically, which was locatedclosely medial to the nucleus of the spinal root of the trigeminal nerve of the
medulla oblongata in two sperm whales and a pygmy sperm whale.
This cell column was observed extending at the level from the obex tothe uppermost medulla in the sperm whale and at the level of the middle one
third of the medulla oblongata in the pygmy sperm whale.
After the precise comparative anatomical and histological investigations,the author has come to the conclusion that the cell column is thought to be
the structure corresponding to the lateral cervical nucleus which has highly
developed in the level of the medulla oblongata.
INTRODUCTION

In the previous report (1977) of a noteworthy cell group located closely medial to
the nucleus of the spinal root of the trigeminal nerve in the sperm whale, the author
pointed out the high possibility that the cell group might belong to the spino-bulbothalamic relay system because of the striking similarity between the characteristicsof the cell group and those of the lateral cervical nucleus.
While Matsumoto (1953) described a specific cell group situated closely medial to the nucleus of the spinal root of the trigeminal nerve in the pygmy sperm
whale. He thought the cell group might belong to the sensory trigeminal nucleus
because of the partial continuance of the gray substance at the oral level of thecell group to that of the spinal trigeminal nucleus.
In this research, the author investigated comparative anatomically and histologically the specimens of two sperm whales and a pygmy sperm whale, andfound out that the cell group Matsumoto described in the pygmy sperm whale
showed just the same characteristics as those of the cell group reported by theauthor in the sperm whales.
MATERIALS AND METHODS

Two adult sperm whales (Physeter catodon Linnaeus) were parts of those which
had been collected by Dr T. Kojima when he was on a whaling expedition in theSci. Rep. Whales Res. Inst.,

No. 35, 1984, 47-56

SEKI

48

Antarctic Ocean in 1949-50. The first sperm specimen was the portion covering
almost full length of the medulla oblongata and the first cervical cord, and thesecond sperm was the part, extending from the level 10 mm above the obex to thatpart which included the first cervical cord. Both materials, after having been preserved in formalin, cut off to meet the purpose, and refixed in Muller's solution in
37°0 for 2 to 3 weeks and mounted in celloidin through the usual manner. Serial
sections of 30 to 45 µm in thickness, along the transverse plane for the first sperm,
and the horizontal plane for the second sperm, were made. Each 5th sections(the first and sixth and so forth with the last order of each figure being 1 and 6)ML3.,.....-

4
~

*

.·
ML
Fig. 1. Approximate location and size of the cell column in question projectedfrom transverse sections on the horizontal plane (dorsal view) in the lst sperm
whale, Kliiver-Barrera, X 3, Arrows show levels: 1 =Plate 1, Fig. 1, 2 =Plate 1,
Fig. 2, 3=Plate 2, Fig. 3, 4=Plate 2, Fig. 4, 5=cranial end of the nucleus of theposterior funiculi, 6=caudal end of the inferior olive, 7=level of the obex, 8=
cranial limit of the dorsal roots. *: Cranial extension of the lateral cervicalnucleus. ML: Midline, FRh: Fossa rhomboidea.
Sci. Rep. Whales Res. Inst.,
No. 35, 1984

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SPECIFIC CELL COLUMN IN PHYSETERIDAE

were stained by the Kltiver-Barrera's method and each 10 sections (lOth, 20th,
30th-etc.) were treated by the Weigert-Pal's or Kultschitzky's method for myelin staining. Silver impregnation method was also applied sporadically on some
sections according to needs.
The pygmy sperm (Kogia breviceps Blainville) whale specimen was a casewhich had been collected by Dr T. Ogawa in 1937 at Shiogama, and the wholebrain stem was treated into the serial section preparates stained by the Pal carmin
method at the Brain Research Institute of the University of Tokyo.

ML

---1

**

..
..

·! •

..

-~:

-

2

ML
Fig. 2. Approximate location and size of the cell column in question superimposedfrom horizontal sections on the horizontal plane (dorsal view) in the 2nd sperm
whale, Kluver-Barrera, X 4, Arrows show levels: 1=level of the obex, 2=cranial
limit of the dorsal roots. *: Artificial cleft, **: Cranial extension of the lateralcervical nucleus, ML: Midline, FRh: Fossa rhomboidea.

Sci. Rep. Whales Res. Inst.,
No. 35, 1984

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SEKI

RESULTSIn the sperm whales, the cell group in question was found as an evident cell column
extending longitudinally from the level of the obex to the uppermost medulla andlocated closely medial to the nucleus of the spinal root of the trigeminal nerve(Plate 1 and 2).
This cell column was surrounded by the coarse myelinated fibers of the lateralfuniculus and seemed oval, fusiform or club shape in appearance at the transverse
sections, and measured 4.0-3.2 mm in dorso-ventral direction, 1.5-1.2 mm in width
at the midmost level of the column, and extended 21 mm on the left side and23 mm on the right side in rostrocaudal direction (Figs 1 and 2).
Inside the cell column, it was filled by rather dense net of fine myelinatedfibers, and some of small bundles of coarse fibers were seen penetrating longitudinally through the gray substance of the column. Such penetrating fiber bundles
were observed numerous in the caudal levels and decreased in number graduallyin the higher levels of the column (Plates 1, 2 and 5, Fig. 9).
Nerve cells contained in the column were thought to be classified in two
types; one was quite numerous and middle sized, somewhat rounded polygonal orsometimes spindle shaped, measured 60-40 µm in long diameter and 40-20 µm in
short one, enclosed fine Nissl granules and stained in light colour, the other one wasless in number and a little smaller in size, measured 50-30 µm in long diameterand 25-18 µm in short one, triangle or multipolar in shape, usually stained darkly.
These cells were disseminated almost evenly in the cell column and they scarcely
made crusters or groups of cells inside the gray substance of the column (Plate 6,
Fig. 11).
These structures noted above were quite characteristic to the cell column inquestion, and made it easy to discriminate from certain other structures in theneighbourhood, i.e. nucleus of the spinal root of the trigeminal nerve, nucleus
ambiguus, nucleus reticularis lateralis etc. (Plates 1, 2, 5 and 6, Figs 11-14).
At the level near the rostral end of the column, although the gray substanceof the column was observed contacting partly with that of the nucleus of the spinal
root of the trigeminal nerve (Plate 1, Fig. 1), identification of both structures was
easily recognized as the characteristics of the nerve cells were different from eachother (Plate 6, Figs 11 and 12).
In the sperm whales, a small lateral cervical nucleus was able to recognize at
the uppermost cervical segment, though less distinct. This nucleus, slender andreticular in appearance, was observed continuous farther cranialwards to the medulla oblongata and finally reaching and fused with the cell column in question at
the level of the obex (Figs I and 2).
In the pygmy sperm whale, the cell group Matsumoto described was observed
as a conspicuous cell column extending longitudinally at the level of the middle
one third of the medulla oblongata and located closely medial to the nucleus of the
spinal root of the trigeminal nerve (Plates 3 and 4 ).
Sci. Rep. Whales Res. Inst.,
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SPECIFIC CELL COLUMN IN PHYSETERIDAE

51

ML

--

-

1

2
3

--4

-

5

6

7

8

ML
Fig. 3. Approximate location and size of the cell column in question projectedfrom tranverse sections on the horizontal plane (dorsal view) in the pygmy sperm
whale, Pal carmin, X 4, Arrows show levels: l =Plate 3, Fig. 5, 2 =Plate 3, Fig. 6,
3=Plate 4, Fig. 7, 4=Plate 4, Fig. 8, 5=caudal end of the lateral recessus, 6=level of the obex, 7=caudal end of the inferior olive B=rostral limit of the dorsal
roots. ML: Midline, FRh: Fossa rhomboidea.

This cell column was surrounded by the coarse myelinated fibers of the lateralfuniculus and seemed oval, fusiform or club shape in appearance at the transverse
sections, and measured 4.2-3.8 mm in dorso-ventral direction, 1.3-1.0 mm inwidth at the level of the obex, and extended 8.8 mm on the left side and 7.3 mm
on the right side in rostro-caudal direction (Fig. 3).
Inside the cell column, it was filled by rather dense net of fine myelinatedfibers, and some of small bundles of coarse fibers were seen penetrating longitudinally through the gray substance of the column. Such penetrating fiber bundles
were observed numerous in the caudal levels and decreased in number graduallyin the higher levels of the column (Plates 3 and 4 ).
Two types of nerve cells were investigated in the column; one was numerous
and middle sized, somewhat rounded polygonal or sometimes spindle shaped,
measured 40-30 µm in long diameter and 30-20 µm in short one, stained in lightcolour, the other one was less in number and a little smaller in size, measured 3020 µm in long diameter and 25-15 µm in short one, triangle or multipolar in shape,
usually stained darkly by the carmin. These cells were disseminated almost evenly
in the cell column and they scarcely made crusters or groups of cells inside theSci. Rep. Whales Res. Inst.,
No. 35, 1984

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SEKI

gray substance of the column.
These structures noted above were quite characteristic to the cell column inquestion in the pygmy sperm whale, and made it easy to discriminate from certain
other structures in the neighbourhood, i.e. nucleus of the spinal root of the trigeminal nerve, nucleus ambiguus, nucleus reticularis lateralis etc. (Plates 3 and 4).
At the level near the rostral end of the column, although the gray substance ofthe column was observed contacting partly with that of the nucleus of the spinal
root of the trigeminal nerve, identification of both structures was easily recognized
as the characteristics of the nerve cells were different from each other.
In the pygmy sperm whale, the lateral cervical nucleus was hardly recognizedat the uppermost cervical segment or the lower medulla in the Pal carmin stained
sections.
DISCUSSION

Dr Matsumoto was the earliest researcher who described the cell column in question. In his anatomical studies on the brain stem of the pygmy sperm whale(1953), he made precise and accurate descriptions on the cell column. Although
he paid attention to the fact that the cells were observed disseminating in the cellcolumn, he thought this column might belong to the sensory trigeminal nucleus
because of the partial continuance of the gray substance at the oral level of thecell column to that of the nucleus of the spinal root of the trigeminal nerve. He
also emphasized that the cell column is a quite exceptional structure to thepygmy sperm whale, and denied such a structure in the dolphin, Sei and Beaked
whales.
In the previous report (1977), present author described a noteworthy cellgroup observed at the level from the obex to the uppermost medulla and locatedclosely medial to the nucleus of the spinal root of the trigeminal nerve, and pointed
out the high possibility that the cell group might belong to the spino-bulbo-thalamic relay system because of the striking similarity between the characteristics ofthe cell group and those of the lateral cervical nucleus.
In this research, specimens of the sperm whales were examined carefully, andfurther, with the permission of the Institute of the Brain Research, University ofTokyo, the serial section preparate of the specimen of the pygmy sperm whale wasinvestigated, which was the case Dr Matsumoto examined before. After the precise comparative anatomical and histological investigations, the author found outthat the noteworthy cell group in question in the sperm whales showed quite thesame characteristics as those of the specific cell group in the pygmy sperm whale
described by Dr Matsumoto, with the exception of the levels of location of thesecell groups; the former was higher in the medulla and the latter was lower and at
the level almost middle one third of the medulla oblongata.
In the previous study on the comparative anatomy of the lateral cervicalnucleus (1965), present author reported that the nucleus was observed at the uppermost cervical segment in the common dolphin (Delphinus delphis Linnaeus), andSci. Rep. Whales Res. Inst.,
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SPECIFIC CELL COLUMN IN PHYSETERIDAE

53

pointed out an interesting fact that the nucleus was extended farther cranialwards
to the lower medulla up to the level of the obex as the gray substances arranged
longitudinally in stepping stone pattern. From the findings of the present investigation, the cell column in question was thought to be locating on the upwards
elongated line of the lateral cervical nucleus, and moreover, in the sperm whales,
the lateral cervical nucleus was found also in the uppermost cervical segment,
though less distinct, and the nucleus was observed continuous farther cranialwards
to the medulla oblongata, as islands-like cell collections in appearance, and finallyreaching and fused with the cell column in question at the level of the obex.
According to these findings noted above, the cell column in question, foundin the sperm whales and a pygmy sperm whale, was considered to be the structure
corresponding to the cell group highly developed in the level of the medulla oblongata showing just the same characteristics as those of the lateral cervical nucleus.
Matsumoto (1953) noted certain degree of asymmetrical development of thecell column in question; the left side column being larger than the right side one,and he thought it might be some relation with the asymmetrical structure of thenasal meatus in the pygmy sperm whale, without an explanation of the reason on
this fact. From the present examination, Matsumoto's finding about the asymmetrical development of the column was reconfirmed distinctly. Ogawa (1949, aand b ), in the pygmy sperm whale, described the striking development of the facial
nucleus of the right side than that of the left side, and suggested that there shouldbe certain relation with the asymmetrical structure of the nasal meatus in thiswhale. Hosokawa (1950) reported some asymmetrical structure of the larynx inthe sperm whale. In spite of the extraordinarily asymmetrical nasal passage, after
the present examination, as far as the extent of the gray substance is concerned,
the cell column in question in the sperm whale was hardly recognized the significant asymmetry. At the present stage of the research, it is thought to be difficult
to say something on the relation between the difference of the largeness of the cellcolumn in each side and the asymmetrical structures of the nasal meatus or thelarynx in these whales.
Matsumoto (1953) stated that the partial continuance of the gray substanceat the oral level of the cell column in question with that of the nucleus of the spinal
root of the trigeminal nerve, and accordingly he thought that the cell column
might belong to the sensory trigeminal nucleus. In the present examination of thespecimen of the pygmy sperm whale, the characteristics of the cell column in question was observed different from those of the nucleus of the spinal root of the trigeminal nerve, and the situation was interpreted as the gray substance of the cellcolumn being in contact with that of the trigeminal nucleus. Concerning this matter, in this research, the structural difference of both gray substances was reconfirmed clearly in the first specimen of the sperm whale, after the examination of
the additional sections treated by the Kluver-Barrera's and silver impregnation
methods.
In the cat or in certain other mammals, it is well known that the lateral cervical nucleus receives afferent fibers originating from the lower levels (Broda! andSci. Rep. Whales Res. Inst.,
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54

SEKI

Rexed 1953, Morin 1955, Ha and Liu 1966, Craig 1978, etc.). Craig (1978) reported medullary input of the lateral cervical nucleus originating from the nucleusof the posterior funiculi and the nucleus of the spinal root of the trigeminal nerve.
Similar relationships, referring the findings of the present examination, could besuggested also in the whales, such as the possibility that a certain amount of fibersof the lateral funiculus might terminate in the cell column.
Although holding a different opinion from that of Dr Matsumoto as to themeaning of the cell column in question, the present author should like to make aproposal, in memory of his first description, to name the cell column as " the nucleus of Matsumoto ", at least for some time until it receives an adequate nomenclature in the future.
SUMMARY

A specific cell column was examined anatomically, which was located closely medial to the nucleus of the spinal root of the trigeminal nerve of the medulla oblongata in two adult sperm whales and an adult pygmy sperm whale.
This cell column was observed extending at the level from the obex to theuppermost medulla in the sperm whales and at the level of the middle one third of
the medulla oblongata in the pygmy sperm whale.
The cell column was surrounded by the coarse myelinated fibers of the lateralfuniculus and bordered in an oval, fusiform or club shape in appearance at thetransverse sections and seemed considerably outstanding from the neighbouring
structures.
Inside the cell column, two types of nerve cells were contained; one was middle sized and polygonal, somewhat rounded or spindle shaped, palely stained, andthe other one was a little smaller in size, triangle or multipolar, stained darkly.
The characteristics of these cells contained seemed very similar to those of thelateral cervical nucleus.
This cell column was thought to be located on the upwards elongated line of
the lateral cervical nucleus and moreover, in the sperm whales, the direct continuance was recognized between the lateral cervical nucleus and the cell column
at the level of the obex.
According to these findings noted above, the cell column in question wasconsidered to be the structure corresponding to cell group highly developed in
the level of the medulla oblongata showing just the same characteristics as thoseof the lateral cervical nucleus.
Although none of the definite finding about the fiber connection of the cellcolumn was obtained, at the present stage of research, it seems there is a high possibility that the cell column belongs to the spino-bulbo-thalamic relay system.
ACKNOWLEDGEMENTS

I should like to express my sincere gratitude to Dr T. Kojima, Professor of
Anatomy, Nihon University School of Medicine, for his kind offering to me theSci. Rep. Whales Res. Inst.,
No. 35, 1984

SPECIFIC CELL COLUMN IN PHYSETERIDAE

55

precious materials (Sperm 1 and 2) for this study. Many thanks are due to Dr
T. Ogawa and Dr T. Kusama, formerly directors of the Brain Research Institute,
University of Tokyo, for their kind permission to my investigation of the researchmaterial (Kogia). Throughout my study on the Kogia, good assistance of Dr T.
Kamiya, formerly a staff of the Department of Anatomy, School of Medicine,
University of Tokyo, is also acknowledged.
REFERENCE
BRoDAL, A. and B. REXED, 1953. Spinal afferents to the lateral cervical nucleus. An experimental study.
]. comp. Neural., 98; 179-212.
CRAIG, A. D., 1978. Spinal and medullary input to the lateral cervical nucleus. ]. comp. Neural., 181;729-744.
HA, H. and C. N. Lru, 1966. Organization of spino-cervico-thalamic system. ]. comp. Neural., 128; 445470.
HosoKAWA, H., 1950. On the Cetacean larynx, with special remarks on the laryngeal sack of the Sei whale
and the arytenoepiglottideal tube of the Sperm whale. Sci. Rep. Whales Res. Inst., 3: 23-62.
MATSUMOTO, Y., 1953. Contributions to the study on the internal structure of the Cetacean brainstem.
Acta Anat. Nippon., 28; 167-177 (in Japanese).
MORIN, F., 1955. A new spinal pathway for cutaneous impulses. Amer.]. Physiol., 183; 245-252.
OGAWA, T., 1949a. Results in recent years in the Cetacean anatomy. Sogo lgaku, 6; 6-11 (in Japanese).
OGAWA, T., 1949b. On the Cetacean brain. Brain and Nerve, 3; 159-165 (in Japanese).
SEKI, Y., 1965. Comparative anatomical studies on the lateral cervical nucleus. Acta Anat. Nippon., 40;(5), Suppl., p. 4 (abstract in Japanese).
SEKI, Y., 1977. On a noteworthy cell group situated medial to the nucleus of the spinal root of the trigeminal nerve in the Sperm whale. Acta Anat. Nippon., 52: 70 (abstract in Japanese).

Sci. Rep. Whales Res. Inst.,
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SEKI

EXPLANATION OF PLATES I-VI
PLATES I AND II
Figs I and 2 and Figs 3 and 4: Transverse sections of the medulla oblongata in the
lst Sperm, arranged from cranial to caudal, Kultschitzky, x 6.
PLATES III AND IV
Figs 5 and 6 and Figs 7 and 8: Transverse sections of the medulla oblongata in the
Pygmy sperm, arranged from cranial to caudal, Pal carmin, X 8.
PLATE V
Fig. 9: The same section as Plate I, Fig. 2, a little enlarged (X 10), left side; note thelocation and shape of the cell column in question and neighbouring structures.
Fig. 10: The section very near to that of Fig. 9, x20, silver impregnation; note thestructural difference of the cell column and the neighbouring nuclei.
PLATE VI
Nerve cells in high magnification ( x 100), Kluver-Barrera.
Fig. I I: The cell column in question.
Fig. 12: Nucleus of the spinal root of the trigeminal nerve.
Fig. 13: Nucleus reticularis lateralis.
Fig. 14: Nucleus ambiguus.

ABBREVIATIONS IN PLATES
FL
FLM
FP
NA
NFP

NQ
NRL
NSV
NXII

OL
RX
RXII

s
TSV

Funiculus lateralis
Fasciculus longitudinalis medialis
Funiculus posterior
Nucleus ambiguus
Nucleus funiculi posterioris
The cell column in question
Nucleus reticularis lateralis
Nucleus tractus spinalis nervi trigemini
Nucleus nervi hypoglossi
Nucleus olivaris inferior
Radix nervi vagi
Radix nervi hypoglossi
Fasciculus solitarius
Tractus spinalis nervi trigemini

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No. 35, 1984

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