transparent with oil of cloves, and mount in Canada balsam or
dammar varnish (see p. 23).
Hidden in the cauda equina is found the filum terminate,
which is the end of the cord. Sections near its end exhibit lit-
tle of the structure of the cord. At a point where it is 1.5 mm.
in diameter it presents the appearance of a peripheral nerve,
except that it has an opening the central canal in its centre.
Its transverse section shows a collection of large and small
myelinic nerve-fibres pursuing a vertical direction.
A little higher up, where the filum measures 2 mm. in diam-
eter, there is little difference, except that the central canal is
nearer the surface (anterior) and surrounded by a small amount
of gray matter. Now and then there are seen small, oval nerve-
cells in the region posterior and external to the central canal.
A little higher still, where the filum is 3 mm. in transverse
and 2 mm. in antero-posterior diameter, back of the central
canal on each side, where the future posterior horn is to be,
there is a small collection of spindle-shaped cells.
Sections from a region a little above this present an entirety
different picture. The gray substance is here much more devel-
oped and occupies the larger part of the section. It is divided
into a club-shaped anterior horn, containing a few large poly-
hedral cells, and a posterior horn which is rounded and formed
of peripherally directed nerve-fibres and oblong nerve-cells.
From this point up sections gradually become more circular
arid develop more and more a resemblance to the structure of
the cord, until, at a point where the sections are about 3.5 mm.
in diameter, the anterior fissure and posterior septum become
well marked. The anterior horns contain few cells, and the
fibres emanating from them pursue a very oblique course down-
ward through the anterior columns.
From the lateral gray matter arise bundles of nerve-fibres
THE CENTRAL NERVOUS SYSTEM.
FIG. 127. Three sections
of the filum terminate: , its
transformation into the coccy-
geal nerve ; 6, section higher
up before the giving off of the
last sacral filaments; c, its
which curve around the posterior horn, and, meeting similar
h'bres from the posterior columns, together form the posterior
nerve-root. These two bundles form an arciform structure sur-
rounding the round extremity of the posterior horn. (See Fig.
127.) The gray commissure occupies one-third the diameter of
the cord. The central canal is large, slit-
like, and antero-posterior in direction. To
summarize then, there seems to be in the
filum terminale, especially its lower por-
tion, a preponderance of the posterior or
sensory part of the cord.
About two centimetres from the end of
the cord nearly the same picture is pre-
sented. The transverse section is circular
and about 6 mm. in diameter. Many large
nerve-cells appear at the outer side of
the anterior cornua, mostly at their junc-
tion with the posterior horns. Fibres from
this cell-group, instead of running a direct course, curve
backward and inward (see Fig. 127), then run forward and
emerge from the anterior horns. Many oval cells appear in
the posterior horns, which now reach the surface of the sec-
tion, and the posterior roots begin to show their origin from
the posterior columns and horns.
In the lumbar enlargement trans-
verse sections have a circular shape.
(See Fig. 128.) The white substance
here predominates, and has but one
peculiarity, which will be noticed in
greater or less prominence through-
out the remainder of the cord. At
the bottom of the anterior fissure is a
broad band of white substance called
the white commissure. This is formed
of myelinic nerve-fibres, which pursue
a course from the base of the anterior
horn of one side, forward, across the
median line and downward to join the
anterior column of the opposite side at a lower level. (See
Fig. 129.) The anterior horns in the lumbar region are large
and square, as are also the cells contained in it. TJie gray
FIG. 128. Three diagrams show-
ing the relations of gray and white
matter in different regions of the cord:
. lumbar enlargement ; 6, mid-dorsal
region ; c, cervical enlargement.
MANUAL OP HISTOLOGY.
commissure is narrow, and the central canal has its long diam-
eter placed transversely to the cord.
Transverse sections in the dorsal region are circular and
8 mm. in diameter. The white commissure is thin, otherwise
the same structure as in the lumbar region is observed. The
anterior horns are narrow and sparsely filled with rather small
multipolar cells. JN~o continuous tracts of nerve-fibres can be
traced through the anterior columns, as their course is so oblique
(downward) as to give almost a transverse section of the bun-
dles. The posterior horns, just behind the gray commissure,
are swollen out, and contain a number of large nerve-cells
some multipolar, some oval. They approach the type of the
cells in the posterior horns. This collection of cells is called the
column of Clarke.
Transverse sections in the cervical enlargement measure
about 14 mm. The antero-posterior diameter is about 11 mm.
The white commissure in this region presents about the same
characteristics as in the lumbar region. The anterior horns are
fan- shaped ; the anterior roots
curve forward, outward, and
downward. The central canal is
triangular. The posterior horns
are slender, and contain a few
small nerve-cells. The posterior
roots are also more intimately
connected with the posterior
horns than lower down.
In the upper cervical region
the gray matter assumes more
the shape of the dorsal gray
matter. In the lateral region, at
the junction of the anterior and
posterior horns, longitudinal bun-
dles of myelinic nerve-fibres begin to appear. These bundles
curve over (see Fig. 129), and pass rather obliquely upward
and outward through the lateral columns, emerging nearer the
posterior than the anterior horns. They are joined by fibres
curving back from the cells of the anterior horns, and also
emanating from the central gray matter. In this structure is
seen the first appearance of the spinal portion of the spinal
accessory root-fibres. The longitudinal bundles mentioned
FIG. 129. Diagram of transverse section of
the cord in the upper cervical region, showing
coarse connective-tissue reticulum in left half
of diagram, commencing decnssation of the
lateral columns across the base of the anterior
horn into the opposite anterior column, taking
the place of the anterior commissure lower
down, and the root of the spinal accessory, 11 :
A.R. = anterior root ; P.R. = posterior root.
In this figure and in others small crosses must
be understood as nerve-cells.
THE CENTRAL NERVOUS SYSTEM.
evidently come from cells of the anterior horns lower down.
Some of the fibres, passing back from the anterior horns to join
the root, are seen to arise directly from the motor cells.
In taking leave of the cord, the introduction of a diagram 1
showing its regional anatomy, looked at from a physiological
standpoint, is deemed ad-
vantageous. It will enable p
the microscopist to properly
record localized lesions.
In studying the spinal
cord by means of horizon-
tal transverse sections, it is
of the utmost importance,
particularly in pathological
cases, to know which is the
right or left side, and whe-
ther one is looking at the
upper or under surface of a
section. Of so much impor-
tance is this knowledge,
that some means must be
employed to acquire it.
One of the best means is a method devised by Dr. E. C.
Seguin, and published in the translator's note appended to
Schultze' s article on the spinal cord, in the American translation
of Strieker's " Histology," p. 647. He there recommends, be-
fore placing the segment of the cord in the microtome, that a
slight longitudinal incision be made in the right lateral column.
By this means all the sections have a nick in the right lateral
column, and can easily be placed. This method, however, has
many drawbacks. One is that it is a process easily forgotten
during the manipulations. Another more serious drawback is
the fact that, make the incision slight as you can, the resulting
nick often causes extensive fissures and crumbling of the lateral
column or whole section, especially in pathological or over-
The requirements by the new method are two : 1st, the
sections must be nearly horizontal ; and 2d, they must be suf-
FIG. 130. Diagram of transverse section of the
spinal cord : A, anterior median fissure ; P, posterior
median septum ; 1, columns of Goll ; 2, columns of
Burdach ; 8, direct cerebellar column ; 4, crossed pyra-
midal column ; 5. lateral column ; 6, anterior funda-
mental column ; 7, direct pyramidal column ; 8, pos-
terior gray horns ; 9, anterior gray horns ; stippled
part, gray matter ; shaded part, sesthesodio system ;
unshaded part, kinesodic system.
1 Dr. E. C. Seguin : Lectures on Localization, in N. Y. Medical Record, April 27,
1878, p. 323.
MANUAL OF HISTOLOGY.
ficiently well stained and transparent to demonstrate the con-
stituent parts of myelinic nerve-fibres. The mode of determi-
nation depends entirely on the fact that the anterior roots
pursue an obliquely descending course .through the anterior
columns, and for this reason horizontal sections cut the ante-
rior rootlets obliquely. (See Fig. 131.)
What is the natural inference to draw from this fact \ It is
this : let the reader look at the upper surface of a transverse
section of the spinal cord and bring the anterior roots into the
field ; that is, let him look down the anterior column. He
readily perceives that the central ends of the anterior root-
fibres are nearer his eye than the peripheral ends. He sees
that while the central ends are at the focus, the peripheral
ends are beyond the focus, and he needs to bring the eye nearer
to define them. This nearing the focus also gives the fibre-
bundle an apparent peripheral motion, while increasing the
focal distance causes an apparent central motion.
The application of this method to a chance section is easy.
Suppose we examine the anterior
columns of a section and find by
focussing that the central ends of
the anterior root-fibres are farther
from the eye than the peripheral
ends. We will immediately know
we are looking up the cord or at
the under surface of the section.
Now, all it is necessary to do is
to turn over the section, either in
your mind or on the slide, and put
the anterior horns forward. The
section is then in position.
In* sections of the cord where
the anterior roots do not show, the
posterior roots may be used in a similar way, as they, too, pur-
sue a slightly descending course. Their use is not so easy, as
the fibres are short and pursue a slightly wavy course. In
sections or fragments of sections, where neither of these struc-
tures avail, a study of the course of the fibres in the anterior
white commissure will lead to detection. These fibres pursue
a course downward and across the median line, from the base of
one anterior horn into the anterior column of the opposite side.
FIG. 131. Diagram of vertical section
of human cord through the anterior arid
iposterior columns and the anterior horns.
It is intended to demonstrate how a trans-
verse, horizontal section, S, cuts the an-
terior nerve-roots obliquely. (From Ar-
chives of Medicine, August 1, 1879, p. 70.)
THE MEDULLA OBLONGATA.
In sections of the upper cervical region the spinal accessory
roots may be made use of, remembering, however, that they
pursue a course obliquely upward through the lateral columns.
The application of these rules to the medulla will be pointed
out later on.
NOTE. To demonstrate the obliquity of the anterior rootlets, find, by a trans-
verse section, the exact direction of the anterior rootlets, and then make longi-
tudinal sections through the anterior column and horn on this line.
THE MEDULLA OBLONGATA.
In the upper part of the cervical region changes take place
in the arrangement of the elements of the cord transforming it
into the medulla oblongata. The changes are as follows : be-
fore the external signs
of decussation ap-
pear, it is seen that
the fibres of the later-
al columns change
their vertical course
and bend forward and
inward. This fact is
demonstrated by the
oblique sections of
bundles and fibres. A
little higher these
bundles and fibres
can be traced across
the gray matter be-
hind the anterior horn
into the opposite an-
terior column, which is to become by this addition the anterior
pyramid. The decussating fibres take the place of the ante-
rior commissure lower down, and the fibres pass upward and
forward across the median line. The fibres of the anterior
columns do not decussate at all, but give way to and mingle
with the fibres from the lateral columns.
The shape and structure of the anterior horns are about the
same as lower down. The posterior horn expands suddenly at
FIG. 132. Diagram of the medulla, pons, etc., natural size, to
show the direction of sections for displaying the different nuclei
and roota : ll/, line of section to show the early decnssation of the
lateral columns and spinal accessory tract; 11, line of section to
show the spinal accessory tract and decussation of the pyramids ;
11 & 12, region of the spinal accessory and hypoglossal ; 10, pneu-
mogastric; 9, glosso-pharyngeal ; 8, acoustic; 6 & 7. abducens
and facial ; 5. trigeminus ; 4, patheticus ; 3, motor oculi ; c. g.,
corpora quadrigemina ; c. c., crua cerebri.
MANUAL OF HISTOLOGY.
its peripheral extremity into a bulbous termination (see Fig.
133), from which the posterior root emerges. The central gray
matter between the two horns is traversed and intersected by
the decussating fibres from the lateral columns. Numerous pro-
longations from this gray matter spread out into the lateral
columns, presenting a coarse reticulum, called iheformatio
FIG. 133. Diagram of transverse section of
human medulla below external decussation of
pyramids, showing bulbous posterior horns:
F R, formatio reticularis; 11, spinal accessory
root and decussation of the lateral columns.
FIG. 134. Diagram. Decussation of the pyra-
mids, shows decussation of the lateral columns,
the swelling of the posterior horns, the shrink-
age of the anterior horns, the spinal accessory
root 11, and a partial decussation of the posterior
columns behind the central canal.
reticularis. The gray commissure is very broad, the central
canal having its long diameter directed antero-posteriorly.
In sections at the decussation of the pyramids proper, i.e.,
where they are seen to decussate externally, a slightly different
picture is presented. The lateral columns have nearly disap-
peared, having now almost all entered into the decussation,
which is here very broad (see Fig. 134), and presents a peculiar
zigzag appearance from the interweaving of bundles of fibres
from the opposite lateral columns. These fibres, after curving
around the anterior columns for a short distance, seem to dis-
appear by assuming a vertical direction. The club-shaped ex-
tremities of the posterior horns remain, while the rest is pushed
back into the posterior columns, and contains many large cells.
The anterior horns are also displaced backward, pushed
back by the anterior columns increased in size by the addition
of the lateral columns. Hence, the anterior roots have a longer
path through the anterior columns and approach the type of
the hypoglossal nerve-roots seen a little higher up. (See Fig.
135.) The spinal accessory nerve curves out and back from the
lateral gray matter where a group of cells is situated.
THE MEDULLA OBLONGATA.
Let us next take up a section involving the lower end of
the olivary body. We have the following view presented.
The section is slightly cordiform. (See Fig. 135.) The decussa-
ting fibres at the base of what remains of the anterior fissure,
which has all along become shallower, now forms the com-
mencement of the rapke, a structure which extends all through
the rest of the medulla and pons, separating the two motor
tracts. The union of the lateral and anterior columns now
nearly complete, forms the anterior
pyramids. The fibres here have a
general vertical direction, except
that a broad band which emerges
from the decussation at the bottom
of the anterior fissure, curves around
the margin of the anterior pyramid,
and then, sometimes in the sub-
stance, sometimes at the surface of
the medulla, almost completely sur-
rounds it, the bundle becoming lon-
gitudinal on the posterior surface.
These bear the name of the arciform
fibres. The rest of the white matter
is so cut up as to render it hardly
divisible into regions. The central canal, which is very long
antero-posteriorly, has almost coalesced with the gradually
deepening posterior furrow soon to become the fourth ventricle.
The gray matter originally in the cord is now collected
about the central canal. Anterior and external to the central
canal there is a small group of multipolar cells. This is the
remnant of the anterior horns, which have been continually
crowded back by the accumulation of fibres in the anterior
pyramids. These cells in every respect are similar to those in
the anterior horns. Their processes give origin to fibres which
course forward in two or three bundles through the white
matter of the anterior pyramids, and emerge at about the
junction of the anterior pyramids and the lateral white mass.
A little farther back in the gray matter, behind the central
canal, is a small group of nerve-cells the remains of the spinal
accessory nucleus, from which a few fibres run in a straight
course outward and slightly backward, through the lateral
white matter. Additional collections of gray matter now begin
FIG. 135. One half of section at lower
end of the olives : 11, upper spinal acces-
sory root ; 12, lower hypoglossal roots.
310 MANUAL OF HISTOLOGY.
to appear. In the posterior region is a large tract (see Fig. 135)
containing scattered groups of many small cells evidently con-
nected with the arcit'orm fibres. This is probably a part of
the lower origin of the pneumogastric. A little in front and
external to this is a small group of larger nerve-cells which
help to form the lower sensory origin of the fifth nerve. Still
farther forward in the lateral region is a large collection of
multipolar nerve-cells. Although this group is traversed in
many directions by fibres, single and in bundles, still it seems
to give rise to fibres which run back and upward, evidently to
curve upon themselves and join the peripheral fibres of the
spinal accessory root. (See Figs. 135 and 137.)
Farther forward still there is a collection of small cells
arranged in a wavy line (see Fig. 135), the commencement of the
olivary nucleus. Through this the roots of the hypoglossus
all pass. Some seem to be lost in it, others appear to arise
from it, but this is probably due to the arrangement of roots
often seen to curve into the nucleus and then out again. As
this is the first appearance of the olivary body, it will be well
here to describe it.
THE OLIVARY BODY.
The olivary nuclei are situated in the medulla, under the
oval projections on its anterior surface called the olivary bodies.
The nucleus consists of a strip of gray matter arranged in gen-
eral like. a piece of fluting folded on itself, so as to form almost
an ellipse. From the concavities of the fold on either side pro-
ceed bundles of fibres, the external ones joining the formatio
reticularis, the internal ones passing into the raphe. Their
connection with the hypoglossal roots is probably not im-
portant. The intimate structure of the olivary fold is that of a
dense gray matrix holding numerous small polyhedral cells
having delicate protoplasmic processes.
Let us now go a trifle higher (see Fig. 137), and observe that
in sections the central canal, which has all along been elongat-
ing and receding backward, now opens into the apex of the
fourth ventricle. There is now, therefore, quite a deep notch in
the posterior part of the section, covered with the same cylin-
drical epithelium which lined the central canal. On each side,
THE OLIVARY BODY.
and in front of the bottom of the fourth ventricle, lies a large
group of multipolar cells, the Jiypoglossal nucleus, from which
bundles of fibres course forward through the olivary body,
which is here much enlarged and more complex than in the
last section. On the inner side of the hypoglossal roots in
the olivary region is an elongated mass of gray matter con-
taining small cells, called the parolmary nucleus. There is
an oval group of fusiform cells at, behind, and external to
the hypoglossal nucleus, from which indistinct and broken
bands of fibres pass outward to emerge from the lateral re-
gion of the medulla. This constitutes the upper spinal acces-
sory nucleus and root. Behind this nucleus, forming the
FIG. 136. Diagram showing structure of
one fold of the olivary nucleus : C, centripe-
tal fibres ; P, peripheral fibres, x 64.
FIG. 137. One-half transverse section of
the human medulla at the point of fusion of
the central canal and the posterior fissure to
form the-fourth ventricle : 11, spinal acces-
sory root ; 12, hypoglossal root ; B, raphe.
eminence on each side of the fourth ventricle, is a large mass
of gray matter containing a great number of small nerve-cells,
which also seems to be rather indistinctly connected with
the spinal accessory root. External to this nucleus is a con-
tinuation of the collection of large cells seen in the section
lower down, the lower sensory nucleus of the fifth. In front
of the spinal accessory root is seen a group of multipolar cells
not so large as in preceding sections. The peripheral circular
fibres in this region are confined to the anterior and external
aspect of the medulla, and are still seen to be in connection
with the raphe by the arcuate fibres which traverse obliquely
the intervening nervous tissue.
From this point to the middle of the olives, sections differ
MANUAL OF HISTOLOGY.
FlG. 138. One-half transverse section of the
human medulla through the middle of the olives :
4, fourth ventricle ; 10, pueumogastric root ; 12,
little, except that in this space the root-fibres of the spinal
accessory seldom appear, although figured by most writers.
The region formerly occupied by the spinal accessory nucleus
contains a group of small cells which form part of the pneu-
mogastric nucleus. The fibres
between this nucleus and the
point of exit of the pneumo-
gastric root run so obliquely
upward, that no direct connec-
tion between them can be traced.
It is in sections at the mid-
dle of the olives that the pneu-
mogastric begins to appear dis-
tinctly. Most of its fibres seem
to be connected with a small
group of cells situated in the
PTaV matter, at the lUnction of
O y <i
the funiculi graciles and the
restiform body. The gray mat-
ter of the restiform bodies is filled with small cells and con-
tains many fibres having a peripheral direction posterior to the
pneumogastric root the beginning of the auditory nucleus
and root. The olivary body here reaches its highest develop-
ment and greatest dimensions.
Behind the olivary body is a small group of cells, from
which scattered fibres pass backward and
inward toward the pneumogastric nucle-
us. But most of them are lost by as-
suming a longitudinal direction. This is
probably the lower facial nucleus, to be
described farther on. The arcif orm fibres
are chiefly confined to the surface of the
anterior pyramids and the olivary bod-
ies. The fibres of the raphe pursue, in
. -,. ,. Fio. 139. One - half trans-
great part, an antero-posterior direction, verse section of the human me -
ci . ,-\ i,,i in 111 dulla through the upper part of
Sections through the medulla at the the olives bringing the giosso-
/, ,, ,. IT- z'jx pharyngeal tract (9.) and the
upper part of the olivary bodies diner lower part of the acoustic nucleus
-i-i . T- (80 into view.
little from the former sections. But a
small segment of the olivary bodies is present, and only a few
of the hypoglossal roots remain. (See Fig. 139.) External to the
remains of the hypoglossal nucleus is a nucleus of small cells
THE OLIVARY BODY.
giving origin to a bundle of fibres, which pass out laterally just