after having extended over a certain length of the ganglion, penetrate
into the substance of the inferior ventral lobule (Cut 2). In transverse
sections (Cut 23) we find the two ventral lobules placed beneath the two
columns which they help to support, and into which they gradually merge;
and we also perceive the transverse commissure which joins the two.
We shall call this the _transverse commissure of the inferior ventral
lobule_.
Let us now pass on to the examination of the upper surface of the
ventral column. This surface is covered by a cluster of very fine fibrils
rather sparsely disposed; we can clearly follow their course by means
of a longitudinal section (Cut 17); we see them again in a horizontal
section (Cut 5). To continue the general description of the ganglion we
must now consider the dorsal region. It is, as we have previously stated,
occupied by a fibrillar substance not so dense as that which composes the
ventral column, and we will give the general name of dorsal lobe to this
region, reserving the name ventral lobe for the region which embraces the
ventral column and its adjoining parts. The dorsal lobe presents as its
distinctive characteristic the feature that it is crossed longitudinally
by a succession of connective filaments clearly seen in the longitudinal
section of Cut 16.
We have already stated that the ventral column receives fibres issuing
from the ganglion in front and sends out others to the ganglia in the
rear. We shall call the totality of these fibres _the connective ventral
filaments_, and shall call the totality of those that traverse the dorsal
lobe _the dorsal connective filaments_.
The connective filaments which join the sub-œsophageal to the first
thoracic ganglion, and which, between these two ganglia, are composed of
a dense fasciculus of fibres, distribute these fibres, at the point at
which they enter the prothoracic ganglia, in different directions; one
set of fibres proceeds towards the ventral column, these are the ventral
connective filaments; a second set traverses the dorsal lobe, and are the
dorsal connective filaments.
Whilst the ventral connective filaments soon merge into the very dense
substance of the ventral column, the dorsal connective filaments, on
the contrary, remain distinct from the organs which they traverse, and
preserve their individuality throughout. They take directions in three
different planes (see Cut 16), consequently they can be subdivided into
superior, medial, and inferior dorsal connective filaments.
Newport seems to have observed this distinction of fibres; and he has
given the name of sensory column to this first division, and that of
motor column to the second. Unfortunately the drawings and figures he has
published, though schematically correct, are not clear. We do not adopt
his terminology, in the first place because he designates the organs
after their supposed functions, and we have made it a rule never to use
controvertible physiological suppositions to designate anatomical organs;
and besides, though the name of column is applicable to the connective
ventral filaments, we cannot apply it to the connective dorsal filaments,
which are subdivided into three pairs of fibrous fasciculi and do not in
the least resemble a column.
In the study of _Melolontha vulgaris_, we have been able to establish in
the most absolute manner that there exists a considerable histological
difference between the connective filaments of the ventral region and
those of the dorsal. Though we have not yet noticed this difference in
_Rhizotrogus_ in any marked degree, nevertheless it has seemed to us
needful to point it out here, because the fact is of such vast importance
that it cannot fail to be general. The dorsal connective filaments,
whilst they preserve their individuality in their passage across the
dorsal lobe of the ganglion, penetrate nevertheless into some small
masses of dotted substance which are found in the path of their entrance
into the ganglion. The mass annexed to the inferior dorsal connective
filament, is above all very important and is directly connected with
the ventral column. As the connective filaments are in pairs, each of
these possesses a distinct mass of fibrillar substance and both the
masses attached to the same pair of connective filaments are joined by a
commissure.
Let us now say a few words about the nerves which proceed toward the
prothoracic ganglion. There exists here but one single pair of nerves,
extremely important and very extensive. This is the crural nerve. To
this nerve are attached the organs which are superadded to the primary
structure of the ganglion, such as we have described it, and which in
consequence renders the primitive structure more complex. We shall
perceive the importance attached to the idea of a _superadded_ organ,
when we study the abdominal ganglia, where the organs we are about to
describe are either completely wanting or are but imperfectly developed.
If now we examine a transversal section taken a little in front of the
place from whence the crural nerves emerge (Cut 19), we shall notice
that the central part of the ganglion is occupied by the ventral column
and the upper part by the dorsal lobe. In addition to this, in the
lateral regions of the ganglion we find two important masses of fibrillar
substance. At this point these two masses remain distinct from the parts
we have just mentioned, and on the other hand they are in connection with
the crural nerves. The latter send a part, and unquestionably the greater
part, of their fibres into the lateral lobes. In a section slightly
posterior to the preceding one, also transversal, a very important change
has taken place; the two lateral lobules, always connected with the
crural nerves, have also established connections with the centre of the
ganglion, and in the sections further on the fusion is complete. As these
lateral lobules possess the characteristics mentioned, only at the point
at which the crural nerves emerge, we shall call them the _crural lobes_.
Thus we find in the prothoracic ganglion three principal lobes: (1) the
crural lobe, which is double, symmetrical, and lateral, (2) the dorsal
lobe, (3) the ventral lobe. These two last, in contradistinction to the
crural lobe, will be classed together under the common term _central
lobe_.
And now to finish this summary description of the prothoracic ganglion,
we will point out an important disposition of the connective tissue which
divides the ganglion into two halves, one anterior, the other posterior.
We can easily understand this disposition by looking at a longitudinal
section passing exactly through the median line. From the dorsal surface
of the ganglion, may be seen descending a bundle of cells and connective
fibres, which, in the form of a column, are directed toward the centre
of the ganglion; these cells and fibres do not meet any important organ
on their way, the dorsal connective filaments always taking a lateral
course. A fasciculus, similarly composed of cells and conjunctival
fibres, starting from the ventral surface of the ganglion, appears
to meet this conjunctival column (Cut 18). This curious disposition
appears to be, as M. Henneguy has ingeniously suggested to me, a trace
of the anterior development of the ganglion which had been formed of two
distinct portions that have been naturally _welded_ together along the
median line; the connective fasciculi corresponding to the point where
the welding has been incomplete, and representing the survival of a
portion of the walls of the two ganglia.
III.
As the ganglion which we have just described contains some structural
difficulties not easy of comprehension, let us proceed with our
description under another form, following the order of our illustrations.
Figure 1 is the first horizontal section, cut through the ventral region
of the ganglion; the knife has here met the lower ventral lobule, which
at this point shows itself double; the two halves being joined by a
double transversal commissure. Section 2, made at a point a little higher
than the preceding one, shows us at the centre the lower ventral lobule
as increased in size; and in the lateral part of the figure appears a new
organ, the crural lobule, which is here entirely merged into the lower
ventral lobule. The crural lobule is traversed by fibres from the crural
nerve, which instead of being entirely lost in its substance, proceed
still further, passing into the lower ventral lobule. Section 3 merely
brings into prominence an important transversal commissure. In Section
4, the inferior ventral lobule is replaced by the ventral column, which
appears double, is symmetrical, and united by a transversal commissure;
this commissure being formed of fibrillar substance. The ventral column
is closely connected on each side with the crural lobule; it is besides
crossed by the ventral connective fibres, which can be seen emerging
from its anterior and posterior extremities. Section 5 allows us to
examine thoroughly the disposition of those ventral connective fibres; we
see that while they penetrate the ganglion, they also pass through two
symmetrical masses of fibrillar substance; these two masses, which we
name the anterior ventral lobules, are joined together by a transversal
commissure. After having traversed the anterior ventral lobules, to which
it appears they give a portion of their fibres, the ventral connective
filaments pass through the ganglion in an antero-posterior direction, and
we see them penetrating the two posterior ventral lobules. The last named
lobules, which remind us by their position and appearance of the anterior
lobules, receive in addition fibres issuing from the crural lobules; but
they do not receive them all, because we notice quite a number of these
fibres advancing directly into the second thoracic ganglion. After
emerging from the posterior ventral lobules, the ventral connective
filaments pass into the second thoracic ganglion, where we see them
penetrate into the anterior ventral lobules.
With Figure 6, we leave the ventral lobe of the ganglion and come
to the lower portions of the dorsal lobule. The important filaments
crossing this section from the front to the back are called lower dorsal
connective filaments. We notice as they proceed some small masses of
dotted substance, and, in addition to these, dark colored dots which are
the result of the knife having cut crosswise through several fascicles of
ascending fibres. We shall find out by means of the sections taken from
different parts and placed so as to allow of our better observation, what
these ascending fibres are. The crural lobule, always exhibits the same
characteristics. We have given it a homogeneous aspect in our drawing. As
a fact it presents in its sections a vast number of structural details.
But these details being very difficult to understand, we prefer not to
dwell upon them.
Section 7 passes through the very midst of the lower dorsal connective
filaments; these filaments being in two pairs, one external and the
other internal. The external pair, situated somewhat lower, has here
disappeared, and the inner pair is the only one to be seen. Some
transversal fibres, whose direction appears to me difficult to follow,
divide the inside dorsal connective filaments at two different points,
and assume the figure of a square; this square has two black dots,
produced by the section of the ascending fibres.
A little higher, in Figure 8, the lower connective filaments have
disappeared and the fibrillar substance of the ganglion is furrowed by
long transversal fibres, of which a part seems to serve the function
of joining the two crural lobules, whilst the remainder, proceeding
towards the black dots before mentioned, continue their progress with
the fasciculi of ascending fibres. These are no other than ascending
fibres which, having changed their direction at the plane of the section,
proceed almost in a horizontal plane. In Section 9 we follow the course
of the medial dorsal connective filaments, separated from the lower
connective filaments by the fibres having a transverse direction, seen
in Figure 8. The medial dorsal connective filaments are four in number,
an outer pair and an inner pair. At the moment when they leave the
prothoracic ganglion, they cross a region where the fibrillar substance
is both thicker and darker. In Figure 10 the medial connective filaments
are on the point of disappearing; they receive certain fibres coming from
the crural lobules, which are now reduced in dimensions. Section 11 shows
us the lower dorsal connective filaments, which are the slenderest of all
and of which there are but one pair; the crural lobule now disappears. In
the middle of the figure, we observe a small collection of conjunctival
cells which, as we have supposed, indicates the point where in the course
of development the two symmetrical portions of the ganglion have not been
perfectly fused together. Finally Section 12 shows two lateral masses of
fibrillar substance, separated by a strip of conjunctival membrane.
We will now take up the series of longitudinal sections, the study of
which will demand very special attention. We shall there meet again with
the organs which we have already examined in the horizontal sections;
and we shall perceive that the alterations and modifications presented
to us by the difference in our point of observation, bring out very
important changes in the appearance of those organs. The sectional method
of examination is also one of analysis. In order to reconstruct an organ
in its complete form and to conceive of it in space, our mind must bring
into a single focus what the sections have represented in a fragmentary
manner: we must, in short, substitute synthesis for analysis.
Figure 13 represents the first and exterior longitudinal section; it
hardly touches the ganglion; in the front we see the starting point of
the crural nerve, and also a portion of the periphery of the crural
lobule. The crural nerve exhibits several roots, the most important of
which occupy the ventral region. Figure 14, though very elementary,
brings out many important points; we see here the crural lobule, which
has increased in size and extends from the ventral to the dorsal region;
a fact which has already been indicated in the horizontal sections, the
crural lobule having been shown in them at all points. This lobule is
almost circular in form. Along its ventral region, we perceive some of
the fibres of the crural nerve which do not penetrate into the lobule;
these are the ones we met with in the figures 2 and 3: they are the
fibres which pass directly into the lower ventral lobule. With Section
15, we leave the lateral regions of the ganglion and come to the dorsal
and ventral regions; we must notice that the crural lobule is continuous
with the central fibrillar mass and has no precise limits. In Section
15 the ventral column appears, reduced in size. In the front of it
we observe an incisure through which certain nerve-cells send their
prolongations into the fibrillar substance.
Figure 16 shows us the complete junction of all the connective filaments
traversing the ganglion; first the ventral column, with the connective
ventral filaments starting from both its extremities; and then the three
dorsal connective filaments, which preserve their individuality distinct,
while they cross the dorsal lobe of the ganglion. The lower dorsal
connective filament is distinguished from the others by a small compact
mass of fibrillar substance through which it passes. We must note that
the fibrillar substance becomes thicker at the point where the whole
series of connective filaments enter the ganglion, and the same thing
is repeated at the place where they leave the first thoracic ganglion
to enter into the second. The ventral column is distinguished from the
other parts of the ganglion by the dark color which it assumes through
the action of the osmic acid; it presents black granules which, examined
with a strong lens, show small fasciculi of fibres running in a parallel
direction. The cells which line the lower surface of the ventral column
do not throw out any prolongations; they are exceedingly small, but do
not otherwise present any special feature.
Figure 17 is but very slightly different from the preceding one: the
ventral column is simply strengthened on its lower surface by the lower
ventral lobule. The position of this lobule is interesting to note. We
have already mentioned that each ganglion is divided into two halves by
a column of conjunctival tissue, one anterior and the other posterior.
In Section 17 we see the granulated projection of the ventral portion
of this conjunctival column. In order to simplify it we have shown no
conjunctival tissue in our illustration. We may nevertheless notice,
that the nerve-cells at the point marked _c. c._ seem to separate one
from the other, and show a triangular space between them, filled with
conjunctival cells. If the segment had not been cut so obliquely, (and
this obliqueness in the sections is almost unavoidable when dealing with
such very small organs,) we should also perceive on the dorsal line
of the section the projection of the dorsal part of the conjunctival
column; in fact we shall see this projection in the figure which follows.
The presence of the conjunctival column separates, as we have said,
each ganglion into two parts, one anterior the other posterior. These
portions are not at all symmetrical. We see in Section 17 that the lower
ventral lobule is found only in the anterior part. Finally from the
ventral column rises an important fasciculus of ascending fibres, which
we have already seen in the horizontal diagrams; it is difficult for
us to ascertain what these fibres are. In the 18th and last section we
approach nearer the median line. The ventral column at this level has
the appearance of being divided into two trunks. The ventral connective
filaments are clearly seen upon its upper surface. Among the dorsal
connective filaments the middle one alone remains visible and receives a
certain number of fibres from the ascending fasciculus.
To complete our description let us glance at the series of transverse
sections. In Figure 19 the two crural lobules have not yet united and
are not yet merged into the dorsal-ventral lobe. This junction does not
take place until we come to Figure 20. Here, at this level, we see in
addition the circular segment of the two ventral columns, which by their
dark color are sharply outlined against the remainder of the fibrillar
substance. To the right and left of these two columns we perceive small
masses of dotted substance; we merely call attention to them and shall
not describe them. Figure 21 furnishes no noteworthy modifications of
the preceding. We simply see a few cells of the periphery sending out
their prolongations into the fibrillar substance. The point at which they
thus penetrate it has already been indicated in Figure 15. In Figure 22
we have a section of several dorsal connective filaments; among others
a lower root of the crural nerve is here seen to pass along the ventral
surface of the fibrillar substance without penetrating into the crural
lobule. Does there exist an upper root of the same nerve, which follows
the upper surface of the dotted substance? We do not dare to decide the
question. One thing is certain, and that is that if the nerve does exist
it is accompanied along its path by a great number of widely ramified
tracheæ, of which we see a drawing in _tr._ In the three figures which
follow (23, 24, 25) the ventral column presents an interesting series of
modifications. First of all, in Figure 23, it is surrounded by the lower
ventral lobule, of which the two masses are in a lateral position, and
whose commissures pass underneath the column. We see in the same Figure
23 the two lower roots of the crural nerve, advancing towards the column.
In the 24th section the two roots have reached the column, and two other
nerves cross the crural lobule; doubtless their destination is the lower
dorsal connective filaments, but of this we have no clear indication.
In the 24th section two other crural roots also enter the lower ventral
lobule. This section is very favorable for the examination of the
ascending fasciculus which we have already noticed in the longitudinal
sections. It seems to us certain that this fasciculus terminates in the
middle dorsal connective filament. Its origin is more uncertain. It seems
to spring from the ventral column, or else to come from crural roots
which, after having traversed the crural lobule, reascend towards the
dorsal lobe of the ganglion, describing a curve exteriorily concave. It
is possible that this ascending fasciculus has both these origins. The
26th and last section shows us the ventral column on a larger scale;
the two columns being distinct from each other, though united at the
lower extremity by a commissure. The _ensemble_ of the figure strikingly
reminds one of a section of the abdominal ganglion.
Here our description ends. We have not sought to follow up every fibre in
all its details, nor to describe completely the anatomy of each organ.
Our intention has merely been to give a synthetic notion of a nervous
ganglion. Subsequent studies made on other ganglia will demonstrate the
general application of this idea.
ALFRED BINET.
FOOTNOTES:
[9] For the cuts, see the plates in the Appendix of this number.
HINDU MONISM.
WHO WERE ITS AUTHORS, PRIESTS OR WARRIORS?
Among all the forms of government class government is the worst. Carthage
was governed by merchants, and the mercantile spirit of its policy led
finally to the destruction of the city. Sparta was governed by warriors,
and in spite of the glory of Thermopylæ it was doomed to stagnation.
India was governed by priests, and the weal of the nation was sacrificed
with reckless indifference to their interests. It appears that for the
welfare of the community the harmonious co-operation of all classes is
not only desirable but also indispensable.
Yet it is often claimed that mankind is greatly indebted to nations or
states ruled by class government, for having worked out the particular
occupation of the ruling class to a perfection which otherwise it would
not have reached. This is at least doubtful.
Carthage was eager to establish monopolies, but she contributed little to
the higher development of commerce and trade among mankind.
Sparta raised brave men, but was not progressive, even in the science
of war, and was worsted by so weak an adversary as Thebes. Modern
strategists could learn something from Epaminondas, but little, if
anything, from the Lacedæmonians.
Priestcraft has attained to a power in India unparalleled in the history
of other nations, and it is no exaggeration to say that priest-rule
was the ruin of the country. Yet the wisdom of the Brahmans has become
proverbial. Their philosophy is praised as original and profound, and it
is well known that the first monistic world-conception was thought out
in ancient India. But we shall see later on what the real share of the
Brahmans in this great work has been.