of those facts. The advisers of Alexander II. did not waste their time
in a hopeless attempt to convert the freedom-worshipping natives of the
Caucasus into devotees of Muscovite despotism, but at once confronted
them with the alternative of exile or death. Our Indian commissioners
early realised the impossibility of turning the descendants of a long
ancestry of deer-hunters into tillers of the soil, and transferred the
survivors of the long race-war to a territory where they could for
better or worse, indulge their incurable penchant. The Groot Fontein
penitentiary of the Transvaal Republic became the grave of so many
Caffirs that the managers at last abandoned the plan of inuring nomads to
the restraints of sedentary occupation, and saved the lives, if not the
souls of their convicts by sending them about in chain-gangs to mend the
irrigation ditches of the border settlements.
Hereditary influences cannot be obliterated by force of rhetoric or of
government edicts and it would solve many riddles if we would apply that
principle to phenomena of ethical and religious evolution. How else
shall we explain the fact that in less than sixty years the doctrine of
Protestantism spread from central Germany to the highland hamlets of
Scotland and Scandinavia, while in Spain, Portugal, and Italy a very
decided progress in general intelligence has failed to lead to a similar
result? How shall we account for the success of Christian missionaries in
Tasmania and Otaheiti and their utter failure in Burmah and Hindostan?
How for the persecution-proof vitality of Judaism, the ready collapse of
Mormonism, or the revival of crass mystic delusions in the midst of our
realistic civilisation?
There is no doubt that the average Spanish sailor, or village-shopkeeper
of to-day possesses a larger stock of general information than the
average Brunswick school-teacher of the sixteenth century. Yet one of the
least learned of those school-teachers could, by instinct, sufficiently
appreciate the significance of the Protestant revolt to celebrate its
triumph by a big bonfire and what our western friends would, call a
“grand war-dance,” on a height near the little town of Wolfenbüttel. Why
does Pedro Gonzales still cross himself at the mention of a heretic,
while Peter Jansen would as soon return to the pig-sty hovels of the
mediæval serfs as crawl back under the yoke of Jesuitry? How could the
bogs of foggy Ireland and the vegas of sunny Spain nourish equally
imperishable roots of a plant that failed to get a firm foot-hold in the
sands of Brandenburgh?
The solution of those enigmas can be found in the circumstance that the
doctrine of anti-naturalism had extended its influence to the character
of many European nations, and that the character-traits of a race are
less amenable to rapid changes than its intellectual standards. On the
soul-organism of the Latin races the thousand years influence of monastic
tyranny has left traces which the light of science will fail to efface
for centuries to come. The propaganda of a manlier creed has thus been
defeated, not only by their ignorance, but by their aversion to mental
efforts, by their habitual reliance on miracles, by their incurable
indifference to the claims of truth and the merits of intellectual
independence, by their hereditary mistrust in the competence of their
natural instinct. To their moral palate a doctrine which nauseates their
northern neighbors has become a pleasant narcotic; they have been forced
to swallow the opium of pessimism till a craving for the repetition of
the mind-enervating dose has become a second nature; they hug the cross
that has proved a symbol of death to their noblest reformers.
Against that influence of perverted instincts the logic of mental
revelations avails but little. “Propositions which would appear
self-evident to certain mental constitutions,” says Dr. Carpenter,
“are apt to be very differently received by others, according to their
conformity or discordance with that _aggregate of preformed opinion_
which has grown up in the minds of each. For just as we try whether a
new piece of furniture which is offered us does or does not fit into a
certain recess in our apartment, and accept or decline it accordingly,
so we try a new proposition which is offered to our mental acceptance.
If it either at once fits in or can by argument or discussion be brought
to fit in to some recess in our fabrics of thought, we give our assent
to it by admitting it to its appropriate place. But if it neither fits
in the first instance nor can by any means be brought to fit, the mind
automatically rejects it.”
It is true that logical demonstrations may become complete enough to defy
dissent, but even from facts which force themselves upon the acceptance
of every rational human being, different individuals will draw widely
different inferences. That the mind of man may become a receptacle for
irreconcilable doctrines is strikingly illustrated, by the simultaneous
acceptance of the Old and New Testament of our heterogeneous scripture,
and in the same way obstinate bigots manage to associate scientific truth
and dogmatic absurdities. Darwin and Moses may occupy adjoining quarters
in the fabric of the same cosmogony; the rule of three may become a
passive concomitant of Trinitarian dogmas. The torch of truth may be
permitted to flicker in a secluded recess of souls which refuse it the
privilege of throwing its rays in certain directions. Education may fail
to reclaim hereditary bigotry. In the winter of 1559 the rabble of Madrid
assembled to witness the death of Don Carlos de Seso, a Spanish nobleman
whose ancestors had fought at Granada and Toledo. His brother had been
the favorite hunting-companion of Charles V.; one of his uncles had
sacrificed his life in deciding the victory of Pavia; Don Carlos himself
had acquired renown both as a soldier and a scholar, but in the latter
capacity he had confessed his sympathy with certain doctrines of Martin
Luther, and the Holy Inquisition had sentenced him to anticipate his doom
in the flames of the stake. King Philip II. honored the _auto da fé_
with his presence, and frowned in a way which the condemned freethinker
mistook for a disapproval of his sentence. “O King! can you thus witness
the torture of your subjects?” exclaimed De Seso. “Deliver us from so
cruel a death which even our enemies admit we have not deserved.” “I
would help carrying faggots to burn my own son,” replied the King, “if
he had incurred your unspeakable guilt.” Yet Philip the Second was one
of the best-educated princes of his century. In mathematics, astronomy,
ancient and modern languages, geography, and history, he was far better
informed than Landgraf Philip of Hessen, who would have risked his own
life to save that of a loyal cavalier.
There are mental mummies who cannot be revived by removing their
grave-shrouds and clothing them in modern drapery; the principle of
conservatism has penetrated their very veins and the marrow of their
bones. It is by no means unconceivable that a popular leader like
Garibaldi or Porfirio Diaz should succeed in persuading a million of his
countrymen to renounce the yoke of Rome and build Protestant chapels, but
the result would be largely limited to a change of nomenclature. Before
long the dissenters would march in procession with a wonder-working tooth
of John Wesley or kiss a shred from the petticoat of the Holy Maid of
Kent. They would groan at the mention of Rome, but exorcise spooks with
the initials of Ulric Zwingli, and abstain from work on the anniversary
of every Protestant martyr. They would try to redeem drunkards by
sprinkling them with consecrated water from the holy rivers of Kansas,
and celebrate Arbor Day only by invoking the spirit of Prof. G. P.
Marsh, as a patron-saint of climate-improving forests. Under the stimulus
of industrial influences, they might transfer the cross from way-side
shrines to telegraph-poles, but they would persist in the worship of
sorrow.
The creed which has turned the happiest countries of our globe into
a grave of their former prosperity, is a medley of miraculism and
anti-naturalism, and the experience of the last century has proved that
both can survive the repudiation of Rome and even of Galilee. The mania
of renunciation, after the abolishment of monasteries and nunneries,
continued its dismal rites in Quaker-garb and Shaker temples of celibacy.
The miracle-hunger of millions who have learned to scorn the clumsy
tricks of the cowled exorcist, gratifies its appetite in the mystic gloom
of the dark cabinet. Rustic supernaturalists, deprived of such luxuries,
indemnify themselves by retailing the marvels of the serpent-charm and
joint-snake superstition.
A curious psychological problem suggests itself in the question how
far the charm of the “sour-grape philosophy” may contribute to the
persistence of certain forms of moral nihilism. Condemned criminals
almost invariably “renounce the vanities” of a life which the Court
of Appeals has refused to save, and in a scaffold-speech, quoted in
Galignani’s _Messenger_ of May 6th, 1837, the English murderer Joseph
Greenacre expressed his conviction that his crime had been the means
of saving his soul, because “death on the gibbet was one of the surest
passports to heaven.”
For similar reasons degenerate nations, after realising the doom of their
national welfare, are apt to renounce the glory of a forfeited world,
and to consider misery, poverty, and shame so many stepping-stones to
the bliss of a better life beyond the grave. After habitual sins against
the health-laws of nature have avenged themselves in cureless diseases,
decrepit bigots may find solace even in that most insane tenet of their
dualistic creed which teaches them to despise the body as the enemy of
the soul.
A natural effect of pessimism may thus, in course of time, become one of
its perpetuating causes.
FELIX L. OSWALD.
THE NERVOUS GANGLIA OF INSECTS.
I.
Although the internal structure of the brain of insects has been the
object of numerous and important investigations, among which we must
place those of Dietl, Flögel, Bellonci, and Viallanes (who have applied
the method of sections to the study of this organ), no attention has as
yet been paid to the other nerve-centres of insects, and in particular
to the ganglia of the ventral chain. Writers have contented themselves
with describing the external form of these ganglia, and their anatomical
relations to the other organic parts; but nothing has been done to throw
light upon their inward structure. All the knowledge which we have on
this subject is very meagre and dates far back to the works of the old
writers, who, like Newport, had at their disposal no other means of study
than the microscopic examination of organs viewed either transparently
or in dilacerated preparations. A method so defective could render but
incomplete results, and indeed in many cases erroneous ones.
We have sought to supply this much to be regretted lack of entomological
knowledge, by applying to the ventral ganglia of insects the admirable
method of sectional cutting, which has brought about such marked advances
in contemporaneous zoölogy.
I need hardly insist on the interest of this research. We shall only
remark that all anatomical study bears an unfinished aspect, up to the
moment at which we grasp the meaning of the organs which we describe;
physiology is a necessary complement of anatomy, it is that which gives
to it a meaning. Therefore, when we dissect an organ, which, as in the
case of an insect’s brain, is endowed with the most complex psychical
properties of which these animals are capable, we find ourselves in the
presence of parts whose functions almost entirely escape us. What is,
for example, that peculiar organ to which we have given the name of the
“pedunculate” body? Anatomists have described with the greatest care its
connections and portrayed its external contour; but we cannot discover,
or even conjecture its uses. It would be necessary to understand the
habits of thought and the feelings of an insect, to be able to assign a
rôle to parts so complex and so delicate as those contained within its
brain.
The study of the ventral ganglia seems to us to be capable of
conducting us to a better result, for in everything that concerns these
nerve-masses, physiology is more advanced, and, in all cases, clearer.
The ganglia of the thorax, for example, are in the main motory centres;
the principal nerves that are sent out from them are to be found in the
wings and in the feet; the study of the terrestrial, aquatic, and aerial
locomotion of insects has already formed the subject of quite a number
of important scientific works; we are now upon well-known ground, and we
may hope that it will be possible to establish some connection between
the anatomical structure of ventral ganglia and the functions which these
ganglia control.
This hope appears to us to be the more legitimate, because we can make
use of all the resources of comparative anatomy to work out the problem.
If we consider any particular function, for example, that of flying,
we notice that in species which resemble each other this function is
exercised under totally different conditions; the same organ acquires
different uses, and these variations become singularly instructive
when we can trace their relationship to the particular structure of a
nerve-ganglion. Thus, one of the large wings of the dragon-fly, which
is almost like a bird in the range and power of its flight, becomes
the elytrum of the beetle; the elytrum is a stiff wing covered by
chitinised matter and serving as a protection to a part of the thorax
and abdomen. Sometimes the elytrum is used in flying, as in the case
of the cockchafer. In other lamellicorn insects, in the _Cetonia_ for
instance, the elytrum is not used in flight; it merely moves aside so
as to allow the second pair of wings to unfold. Its rôle becomes still
less active in the golden carabus, in _Procrustes_, in _Blaps_, and many
other _Coleoptera_, whose two elytra are found on one vertical line,
and form but one single and immovable portion; then the second pair of
wings disappear; from the physiological point of view, the animal becomes
apterous. In another and different order, the order _Diptera_, it is the
second pair of wings that undergo an important modification; they cease
to be used in flying, and are transformed into an organ of equipoise:
they are used for maintaining equilibrium.
All these physiological variations, taking place in the self-same organ,
must in all probability have their counterpart in the internal anatomy of
the ganglion that governs the organ, and the comparative study of this
ganglion in different species will enable us perhaps to discover the
functions of some of its parts. Thus, if we consider by hypothesis, as
the nerve-centre of flight, some small lobe which is found occupying this
or that place in a thoracic ganglion, the disappearance or modification
of this lobe in species not possessing the faculty of flying, might serve
to throw additional light upon such an interpretation.
What we have just said with regard to flight is equally applicable to
terrestrial locomotion, which also represents in itself many varieties.
The typal insect possesses three pairs of feet, whence the name of
hexapods, but there are particular species which drop a pair of feet,
for instance, the _Lepidoptera_ of the genus _Vanessa_; in others,
the physiological function of the foot varies; in the case of the
carrion-beetle (a necrophagus coleopter) it serves as an instrument of
tillage, to dig with; for the cricket, the third pair of feet are used
for the purpose of leaping; for the _Dytiscus_, it serves as an oar, and
so on. We must also bear in mind the curious fact that there exists in
the larvæ of certain insects what are called supplementary feet, having
only a transient existence and disappearing at maturity; the caterpillar,
the larva of the butterfly, has five pairs of supplementary feet. These
notable facts demonstrated by comparative anatomy, cannot fail to furnish
us with valuable information concerning the functions of the complex
organs found in the ganglia of the thorax.
But this is not all. We have not enumerated all the contributions of
comparative anatomy to the problem which we are now about to consider; we
may make use of the method of comparison without bringing the different
types into juxtaposition, but by viewing the nervous system of only
a single animal in its entirety. We know in fact that the body of an
insect is formed by a definite number of segments, all constructed on
the same fundamental plan and arranged in a linear series. Each one of
these segments is joined to a nerve-ganglion, which is all its own and
supplies it with sensibility and motility, the two elementary properties
of nervous activity. In the course of development, these ganglia have the
power of changing their positions; and it is not uncommon to find that
the greater number of the abdominal ganglia move up into the thorax; each
one, nevertheless, retaining its nerve-relationship to its own segment.
Now all the segments of an insect’s body are not called upon to play the
same rôle; a division of labor has been effected among them with regard
to the functions which they are found to exercise: as we have already
seen, the ganglia of the thorax are essentially centres of locomotion;
in the head, one of the ganglia, the sub-œsophageal, furnishes the
nerves of the buccal portions; the other one, the brain, is connected
with particular nerves and becomes the centre of the highest form of
psychical activity of which the creature is capable. We have here a
number of modifications superadded to the original plan. Yet the original
plan should again be met with in the ganglia that have been least
differentiated, such as those in the abdominal region; and the comparison
between an abdominal and a thoracic ganglion, for instance, is well
calculated to show what are the primal and fundamental structures, and
what are the secondary ones which have been superadded and have become
necessary for the execution of the more complex functions. The study
of embryonic and larval forms so easily observed in insects, will most
probably conduct us to the same result. And thus perhaps by continuous
efforts, all guided by the same governing idea, we shall ultimately
arrive at the analogies that exist between the cerebroid ganglia and the
humblest ganglia belonging to the ventral chain, and thus finally be
able to understand the action of the nerve-substance.
The importance of this object, which, be it clearly understood, can
never be attained except by the united effort of many workers, is well
calculated to command our strenuous exertions and to encourage us in
surmounting the difficulties of a study which is as yet almost entirely
new.
II.
We shall restrict ourselves in this article to the consideration of one
particular case; we shall describe a single ganglion of the insect. The
type we have chosen, for reasons too lengthy to enumerate, is a Coleopter
of the family of _Melolonthidæ_; the _Rhizotrogus solstitialis_, a small
beetle very commonly found in the southwest of France. We will now
proceed to the consideration of the first thoracic ganglion.
The prothoracic ganglion in the rhizotrogus is joined by very short
connective filaments to the second thoracic ganglion, and also to the
sub-œsophageal ganglion; this latter ganglion, we must note _en passant_,
being situated in the thorax. If with a pair of scissors we sever the
head of the rhizotrogus, we find that the remainder of the body contains
not only the thoracic ganglia, but also the sub-œsophageal; a peculiarity
which, from a physiological point of view, is very interesting.
The ganglion of the pro-thorax, which is greater in width than it is in
length, bears a vague resemblance to a cone the base of which is turned
towards the sub-œsophageal ganglion, whilst the apex points towards the
second ganglion of the thorax. From the lower part spring two large
nerves, their starting-point being nearer the ventral than the dorsal
surface, a fact clearly comprehended when we find that the fibres of
these nerves extend for the most part into the first pair of feet, that
is to say, into those organs that lie underneath the horizontal plane
of the ganglion. The connective filaments which penetrate the ganglion
anteriorly enter it nearer the dorsal surface than the ventral, this last
being extremely convex. Dissection throws no additional light upon the
anatomy of the ganglion. But by means of a series of sections, we find
that it is composed of a mass of fibrillar substance which occupies its
centre portion and of a layer of nerve-cells surrounding the fibrillar
substance. This fibrillar mass is, owing to its great volume, far the
most important, and constitutes in itself alone about four-fifths of the
organ. The fibrillary structure can only be satisfactorily analysed by
using on it osmic acid, or other equivalent reagents which dissociate
it and admit of its being reduced to a certain number of clearly
differentiated elements. Whenever osmic acid or a similar reagent has not
been employed, or has not sufficiently penetrated the ganglion, owing
to the obstacle presented by a thick conjunctival covering or envelope,
the fibrillar substance takes on a homogeneous aspect that effectually
renders all analysis of it impossible. Everything depends on the
employment of a good method of preparation.
When the ganglion has been properly prepared, we perceive a very material
difference in the appearance of the fibrillar substance when we compare
the dorsal with the ventral region of the ganglion. We can do this
very satisfactorily by a longitudinal section, extending through both
regions. In such a section close to the median line but not confounded
with it (see Cut 16)[9] we perceive that the ventral region is occupied
by a cord or string of substance which owing to the action of the osmic
acid has become very black, and which is formed of so dense a tissue,
that we can with difficulty separate it into fibres and fibrillæ. This
cord, which, by reason of its position and shape, I propose naming the
_ventral column_, extends over the ventral surface of the ganglion in a
longitudinal direction; at both its anterior and posterior extremities it
is carried on by fibres extending into the ventral columns of the other
ganglia, in such a manner that the entire series of ganglia are united by
one continuous ventral cord.
If we look at a transverse section (see Cut 26), the cord, which is
recognised by its dark color and by its position near the ventral surface
of the fibrillar substance, will be seen to have the form of two almost
perfect circles. The ventral column thus presents a circular section, is
duplex and symmetrical: there exist two separate and distinct ventral
columns, separate at least for a certain length; a fact which must be
considered in connection with the primitive duality of the ganglion.
In every section where the columns remain distinct from each other, they
are separated either by fibres and conjunctival cells, or by nerve-fibres
emanating from the cells of the ventral region and proceeding in an
upward direction between the two columns. At the other points, the two
columns join on the median line. This union is effected in different
ways, either by the two columns coming directly together, thus merging
into a single mass, or by a commissure which describes the arc of a
circle underneath the two columns, or else by the inferior ventral lobule.
We give the name of inferior ventral lobule to a small lobule of
fibrillar substance, situated beneath the ventral column. When looked
at in a horizontal section not passing through the median line (see Cut
17), this lobule presents the appearance of a rounded protuberance,
breaking the almost rectilinear contour of the ventral column. As this
characteristic peculiarity is repeated in the internal structure of
all the ganglia, we may use it to ascertain the number of the ganglia,
whenever these present the appearance of being fused into one compact
mass; we may see the practical application of this remark by observing
the sub-œsophageal ganglion.
In a succession of horizontal sections, the starting point of which is
the ventral region, the first mass of fibrillar substance met with by the
knife is the inferior ventral lobule, which is formed (see Cut 1) by two
rounded fasciculi, placed symmetrically on either side of the median line
and joined together by a transverse commissure.