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Observations concerning the comparative anatomy of the diencephalon.

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OBSERVATIOKS COKCERXING THE COMPARATIVE
ANATOMY OF THE DIENCEPHALON
EDWARD 11’. MALOXE
From the Anatomical Laboratory of the University o j Cincinnati
FOUR FIGURES
The purpose of this article is to describe briefly in the diencephalon of the lemur and the cat certain cell groups already
described by me in the human. It will be necessary to give s,
short statement of the different methods of dividing the diencephalor into nuclei, as based upon histological evidence.
A division of the diencephalon based upon histological evidence will vary according to the method of interpretation. Two
methods of division may be recognized :
1. The topographical, by which the diencephalon is divided
into inany fields termed (in many cases erroneously) nucIei.
These fields are for the most part determined by the splitting
up of the gray matter by fiber masses. Such a division according t o the gross, mechanical grouping of gray matter may be
obtained from Nissl preparations as readily as those of WeigertPal, if the cell preparations are studied merely a3 the positive
of the Weigert-Pal negative; unless the cell character is considered, the correspondence of the Nissl picture to that of the
fiber preparation is no indication of the correctness of the resulting division. When so interpreted the two pictures must neeessarily correspond.
2. The second method of division is that employed by me in
my monograph “ Uber die Kerne des menschlichen Diencephalon,” and divides the diencephalon into primary nuclei. A
primary nucleus I have defined as a more or less circumscribed
group of cells having an identical (histological) character. With
our present knowledge we are justified in setting aside a group
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282
E D W A R D F. M A L O N E
of cells as a primary nucleus, only when the histological character of these cells differs markedly from that of the surrounding
cells. And if we take into consideration the fact that certain
purely mechanical influences (such as compression by dense
fiber masses) may change the histological picture of a cell, we
are justified in assuming: that a fairly well circumscribed group
of cells hating a n identical histological character (primary nucleus)
has a d&nite primary function, and further, that two primary
nuclei whose cells show a marked difference in histological character
possess a different primary function. T o sum up: The division
into primary nuclei depends upon (a) an entire indifference to
the splitting up of cell masses by bundles of fibers, and (b) the
bringing together of cells with an identical histological character
to constitute a primary nucleus, even when these cells are intermingled with those of one or more other primary nuclei. The
purpose of such a division is: (a) to prepare a basis for finer
experimental and pathological study, and (b) by the location
of certain definite cell types to enable us to state their function,
even when these cells are not directly accessible to experiment.
I n making a comparative study of the diencephalon of different animals, one is impressed with the great difference in the
structure and grouping of the cells. This difference is greatest
in the thalamus, and since its development depends upon that
of the cerebral cortex, these dissimilarities are to be expected.
T o give an adequate description of the relations between the
thalamus of the cat and of man, would require a careful study
of several intermediate forms. But the hypothalamus is an
older part of the diencephalon, and consequently we find here
better differentiated cell groups, which show comparatively
slight variations in different animals. Therefore it is possible
t o compare certain primary nuclei in the hypothalamus of the
cat and man, with the aid of only the lemur as an intermediate
form. Moreover the recent article of Friedemann on cercopithecus affords further material for such a comparison.
I n addition to the five series of the human diencephalon,
which have been described in a previous article, the present
description is based upon three complete transverse series of
COMPARATIVE ANATOMY O F T H E DIENCEPHALON
283
the cat, and one of the lemur. All series were stained with
toluidin-blue.
The human hypothalamus I have subdivided int,o the following primary nuclei : (1) Corpus hypothalamicum, (2) Nucleus
medialis corporis mammillaris, (3) Nucleus intercalatus corporis mammillaris, (4) Nucleus mamniillo-infundibularis, (5)
Nucleus paraventricularis hypothalami, (6) Substantia reticulark hypothalami, (7) Substantia grisea ventriculi tertii. All
of these nuclei may be identified in the cat and lemur, although
the picture is less clear than in the human.
As some of them have been described only once (in cercopithecus) since their existence was pointed out by me in my
monograph on the human diencephalon, it seems advisable to
mention certain observations, although a thorough description
must await the preparation of further material.
The corpus mammillare in the cat and in the lemur presents
the same nuclei described by me in man, and more recently by
Friedemann in cercopithecus:
1. The ganglion mediale corporis mammillaris, which is cornposed of small cells and occupies the greater part of the mamillary body, is well known and may a t once be dismissed.
2. The nucleus mammillo-infundibularis corresponds in part
probably to the lateral ganglion of the authors. But in addition to forming the lateral portion of the mammillary body,
its cells, which through their histological character can be distinguished from the surrounding cells, extend in a dorsal and
oral direction into the region of the infundibulum. The existence of this nucleus has been confirmed by Friedemann, who
adopts for it the name here given. This nucleus is less well
developed in the cat and the lemur than in man, and does not
stand out so distinctly.
3. The nucleus intercalatus corporis mammillaris is in the
cat and lemur relatively better developed than in man. On
the other hand it is not always so easily distinguished from the
lateral ganglion (nucleus maminillo-infundibularis) . This nucleus consists of a round or oval group of cells, which in its caudal
portion lies on the latero-ventral margin of the corpus mamTHE ANATOMICAL RECORD, VOL.
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284
EDWARD F. MALONE
millare; it extends in a dorso-oral direction between the medial
and lateral ganglion. Whether the nucleus accessorius, which
Kijlliker has described in man, is identical with my nucleus
intercalatus, is doubtful, since according to Kolliker the cells
of the nucleus accessorius are smaller than those of the other
two groups of the corpus mammillare; the cells of the nucleus
intercalatus are on the contrary larger than those of the medial
ganglion. Since Kolliker has not given any accurate description
of these cells, nor of the extent of this cell group, it seems probable that he has described one of the islands of cells often mechanically cut off by a fiber mass from the medial ganglion. Friedemann describes a nucleus intercalatus in cercopithecus, and
adopts this name, after discussing the nucleus accessorius of
Kiilliker.
An exceedingly sharply defined group of cells has been described by me in man under the name of ‘nucleus paraventriculark hypothalami’. It consists of a compact column of large
deeply staining cells, and lies near the third ventricle. It is
well developed in the cat and lemur. Under the same name this
nucleus has been recently described in cercopithecus by Friedemann. It probably corresponds to the nucleo subventricular
described by Cajal in the rabbit. Possibly the nucleus paraventricularis hypothalami corresponds to the nucleus subcommissuralis described by Ziehen in marsupials.
Under the name of substantia reticularis hypothalami may
be classed certain cells of diverse histological character which are
distributed more or less diffusely throughout the hypothalamus.
I t seems inadvisable t o attempt a thorough description of these
cells until more material is available. But one point must be
mentioned, to which I have already called attention in my monograph on the human diencephalon. The hypothalamus of the
cat and lemur, just as in man, is characterized by containing
the only cells in the entire diencephalon of a motor structure.
These cells are similar to the motor cells of the anterior quadrigeminal body, and form a direct continuation of these cells
into the hypothalamup Of course it is not probable that these
cells are part of peripheral neurones ; the modified histological
COMPARA4TIVEANATOMY OF THE DIENCEPHALON
285
picture is against this. But it is highly probable that they are
more or less directly associated with peripheral motor neurones.
This view is strengthened ,by the fact that in the substantia
reticularis of the hypothalamus numerous transition types of
cells occur, from those entirely devoid of motor structure tcj
such as can only with difficulty be distinguished from genuine
peripheral motor cells. Another very significant fact is that
no trace of motor structure can be detected in a n y of the cells of the
thalamus, epi-, or metathalamus, which are exactly those portions
of the diencephalon which are known to contain sensory centers.
CONCLUSIONS
1. Among the cell groups of the hypothalamus of the cat
and the lemur the following primary nuclei may be identified
with similarly named nuclei described in my monograph on
the human diencephalon : (1) Ganglion mediale corporis mammillaris, ( 2 ) Nucleus mammillo-infundibularis, (3) Nucleus intercalatus corporis mammillaris, (4)Nucleus paraventricularis
hypothalami, ( 5 ) Substantia reticularis hypothalami.
2 . Cells of an undoubted motor structure occur in the hypothalamus of the cat, lemur and man. Such cells are entirely
absent from the other divisions of the diencephalon.
BIBLIOGRAPHY
(For full bibliography scc papers of Fricdcmann and myself)
CAJAL,R A M ~YN 1904 Tcstura dcl sistema ncrvioso, etc.
FRIEDEMANN,
M. 1911 Die Cytosrchitcktonik des Zwischenhirns der Cercopitheken mit bcsondcrer Bcrucksichtigung dcs Thalamus opticus.
Journal fur Psychologic und Neurologie, Bd. 18, Erganzungshcft 2.
KOLLIXER,
A.
1806 Handbuch der Gcwcbelehre, Bd. 2 .
MALONE,
E. F. 1910 Ubcr dic Kcrne des menschlichen Diencephalon. Aus dcm
hnhang zu den Abhandlungcn der konigl. prcuss. Akademic dcr
Wissenschaftcn.
Z r n ~ s x , Zcntralncrvcnsystem der Monotremcn und Marsupialer. Zoologische
Forschungsrciscn nach Australicn und dem malayischen Archipel, von
Richard Semon, Bd. 3.
286
EDWARD F. MALONE
EXPLANATION O F FIGURES
The figures represent cross sections through the human diencephalon. Drawings of the cat and the lemur have not been included, since they would necessitate
a more definite expression of facts than would be justified by the amount of material a t present available. The outlines of the drawings were made with aid of
the Edinger drawing apparatus, and the details filled in under control of the
microscope.
The original magnification was 10 diameters. Fig. 1. has bccn reduced t o
3.75, and figs. 2 t o 4 t o 3.3 diameters; the magnification of the cells is much greater.
The drawings show merely the position of the various nuclei, and the arrangement
of the cells within each nucleus.
ABBREVIATIONS
n.mg.th. ( p r . ) , nucleus magnocellularis
com.nied., comissura media
thalami, pars principalis
c.sth. corpus subthalamicum
n.mam.injd., nucleus mammillo-infunf . fornix
dibularis
ggl.hab., ganglion habenulae
ggl.?ned.c.mam., ganglion mediale cor- n.prnd.th., nucleus paramedianus thalami
p p e d h t . , nucleus peripeduncularis laterporis mammillaris
alis (Jacobsohn)
g.0.b.
ganglion opticum basale (so
n.pu.hyp., nucleus paraventricularis hycalled)
pothalami
n.c., nucleus caudatus
n.cs.th., nucleus communis thalami
n.pv.th., nucleus parvocellularis tha1:mii
n.cs.th. (dors.), nucleus communis thal- n.r.th., nucleus reuniens thalami
n.rub., nucleus ruber
ami, pars dorsalis
n.cs.th. (lat.), nucleus communis thalami, s.gr1 111, substantia grisea vcntricuii
tertii, pars inferior
pars lateralis
n.cs.th. (meti.), nucleus communis thal- s. gr2 111, substantia grisea vcntriculi
ami, pars medialis
tertii, pars superior
n.i.c.mam., nucleus intercalatus cor- s.n., substantia nigrtl
poris mammillaris
s.ret.hyp., substantia rcticularis hypothalami
n .mg.th. (arc.), nucleus magnocellularis
t., cells of the telencephalon
thalami, pars arcuata
tr. th. mam., tractus thalamo-mammillaris
THE ANATOMICIL RECORD, VOL.
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PLATE 2
~ O J I P . 4 R X ~ l V ASATOMY
E
O F THE D I E N C E P H A L O S
E U W A R U F. MALOXE
288
COMPARATIVE ASATOMY OF THE DTENCEI’HALOS
EDW’AHD F. h1AI.OSE
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