which was very early adopted; but only gradually unfolded into
distinctness and generality.[54\17] The ancients were acquainted
with the fecundation of vegetables. Empedocles, Aristotle,
Theophrastus, Pliny, and some of the poets, make mention of it; but
their notions were very incomplete, and the conception was again
lost in the general shipwreck of human knowledge. A Latin poem,
composed in the fifteenth century by Jovianus Pontanus, the
preceptor of Alphonso, King of Naples, is the first modern work in
which mention is made of the sex of plants. Pontanus sings the loves
of two date-palms, which grew at the distance of fifteen leagues
from each other: the male at Brundusium, the female at Otranto. The
distance did not prevent the female from becoming fruitful, as soon
as the palms had raised their heads above the surrounding trees, so
that nothing intervened directly between them, or, to speak with the
poet, so that they were able to see each other.
[Note 54\17: Mirbel, _El._ ii. 538.]
Zaluzian, a botanist who lived at the end of the fifteenth century,
says that the greater part of the species of plants are
_androgynes_, that is, have the properties of the male and of the
female united in the same plant; but that some species have the two
sexes in separate individuals; and he adduces a passage of Pliny
relative to the fecundation of the date-palm. John Bauhin, in the
middle of the seventeenth century, cites the expressions of
Zaluzian; and forty years later, a professor of Tübingen, Rudolph
Jacob Camerarius, pointed out clearly the organs of generation, and
proved by experiments on the mulberry, on maize, and on the plant
called Mercury (_mercurialis_), that when by any means the action of
the stamina upon the pistils is intercepted, the seeds are barren.
Camerarius, therefore, a philosopher in other respects of little
note, has the honor assigned him of being the author of the
discovery of the sexes of plants in modern times.[55\17]
[Note 55\17: Mirbel, ii. 539.]
The merit of this discovery will, perhaps, appear more considerable
when it is recollected that it was rejected at first by very eminent
botanists. Thus Tournefort, misled by insufficient experiments,
maintained that the stamina are excretory organs; and Reaumur, at
the beginning of the eighteenth century, inclined to the same
doctrine. {459} Upon this, Geoffroy, an apothecary at Paris,
scrutinized afresh the sexual organs; he examined the various forms
of the pollen, already observed by Grew and Malpighi; he pointed out
the excretory canal, which descends through the style, and the
_micropyle_, or minute orifice in the coats of the ovule, which is
opposite to the extremity of this canal; though he committed some
mistakes with regard to the nature of the pollen. Soon afterwards,
Sebastian Vaillant, the pupil of Tournefort, but the corrector of
his error on this subject, explained in his public lectures the
phenomenon of the fecundation of plants, described the explosion of
the anthers, and showed that the _florets_ of composite flowers,
though formed on the type of an _androgynous_ flower, are sometimes
male, sometimes female, and sometimes neuter.
But though the sexes of plants had thus been noticed, the subject
drew far more attention when Linnæus made the sexual parts the basis
of his classification. Camerarius and Burkard had already
entertained such a thought, but it was Linnæus who carried into
effect, and thus made the notion of the sexes of vegetables almost
as familiar to us as that of the sexes of animals.
_Sect._ 3.--_The Consequent Speculations.--Hypotheses of Generation._
THE views of the processes of generation, and of their analogies
throughout the whole of the organic world, which were thus
established and diffused, form an important and substantial part of
our physiological knowledge. That a number of curious but doubtful
hypotheses should be put forward, for the purpose of giving further
significance and connexion to these discoveries, was to be expected.
We must content ourselves with speaking of these very briefly. We
have such hypotheses in the earliest antiquity of Greece; for as we
have already said, the speculations of cosmogony were the source of
the Greek philosophy; and the laws of generation appeared to offer
the best promise of knowledge respecting the mystery of creation.
Hippocrates explained the production of a new animal by the _mixture
of seed_ of the parents; and the offspring was male or female as the
seminal principle of the father or of the mother was the more
powerful. According to Aristotle, the mother supplied the _matter_,
and the father the _form_. Harvey's doctrine was, that the ovary of
the female is fertilized by a _seminal contagion_ produced by the
seed of the male. But an opinion which obtained far more general
reception was, that {460} the _embryo pre-existed_ in the mother,
before any union of the sexes.[56\17] It is easy to see that this
doctrine is accompanied with great difficulties;[57\17] for if the
mother, at the beginning of life, contain in her the embryos of all
her future children; these embryos again must contain the children
which they are capable of producing; and so on indefinitely; and
thus each female of each species contains in herself the germs of
infinite future generations. The perplexity which is involved in
this notion of an endless series of creatures, thus encased one
within another, has naturally driven inquirers to attempt other
suppositions. The microscopic researches of Leeuwenhoek and others
led them to the belief that there are certain animalcules contained
in the seed of the male, which are the main agents in the work of
reproduction. This system ascribes almost everything to the male, as
the one last mentioned does to the female. Finally, we have the
system of Buffon;--the famous hypothesis of _organic molecules_.
That philosopher asserted that he found, by the aid of the
microscope, all nature full of moving globules, which he conceived
to be, not animals as Leeuwenhoek imagined, but bodies capable of
producing, by their combination, either animals or vegetables, in
short, all organized bodies. These globules he called _organic
molecules_.[58\17] And if we inquire how these organic molecules,
proceeding from all parts of the two parents, unite into a whole, as
perfect as either of the progenitors, Buffon answers, that this is
the effect of the _interior mould_; that is, of a system of internal
laws and tendencies which determine the form of the result as an
external mould determines the shape of the cast.
[Note 56\17: Bourdon, p. 204.]
[Note 57\17: Ib. p. 209.]
[Note 58\17: Ib. p. 219.]
An admirer of Buffon, who has well shown the untenable character of
this system, has urged, as a kind of apology for the promulgation of
the hypothesis,[59\17] that at the period when its author wrote, he
could not present his facts with any hope of being attended to, if he
did not connect them by some common tie, some dominant idea which
might gratify the mind; and that, acting under this necessity, he did
well to substitute for the extant theories, already superannuated and
confessedly imperfect, conjectures more original and more probable.
Without dissenting from this view, we may observe, that Buffon's
theory, like those which preceded it, is excusable, and even deserving
of admiration, so far as it groups the facts consistently; because in
doing this, it exhibits the necessity, which the physiological
speculator ought to feel, of aspiring to definite and solid general
principles; and that thus, though {461} the theory may not be
established as true, it may be useful by bringing into view the real
nature and application of such principles.
[Note 59\17: Ib. p. 221.]
It is, therefore, according to our views, unphilosophical to derive
despair, instead of hope, from the imperfect success of Buffon and
his predecessors. Yet this is what is done by the writer to whom we
refer. "For me," says he,[60\17] "I vow that, after having long
meditated on the system of Buffon,--a system so remarkable, so
ingenious, so well matured, so wonderfully connected in all its
parts, at first sight so probable;--I confess that, after this long
study, and the researches which it requires, I have conceived in
consequence, a distrust of myself a skepticism, a disdain of
hypothetical systems, a decided predilection and exclusive taste for
pure and rational observation, in short, a disheartening, which I
had never felt before."
[Note 60\17: Bourdon, p. 274.]
The best remedy of such feelings is to be found in the history of
science. Kepler, when he had been driven to reject the solid
epicycles of the ancients, or a person who had admired Kepler as M.
Bourdon admires Buffon, but who saw that his magnetic virtue was an
untenable fiction, might, in the same manner, have thrown up all
hope of a sound theory of the causes of the celestial motions. But
astronomers were too wise and too fortunate to yield to such
despondency. The predecessors of Newton substituted a solid science
of Mechanics for the vague notions of Kepler; and the time soon came
when Newton himself reduced the motions of the heavens to a Law as
distinctly conceived as the Motions had been before.
CHAPTER V.
EXAMINATION OF THE NERVOUS SYSTEM, AND CONSEQUENT SPECULATIONS.
_Sect._ 1.--_The Examination of the Nervous System._
IT is hardly necessary to illustrate by further examples the manner
in which anatomical observation has produced conjectural and
hypothetical attempts to connect structure and action with some
{462} higher principle, of a more peculiarly physiological kind. But
it may still be instructive to notice a case in which the principle,
which is thus brought into view, is far more completely elevated
above the domain of matter and mechanism than in those we have yet
considered;--a case where we have not only Irritation, but
Sensation;--not only Life, but Consciousness and Will. A part of
science in which suggestions present themselves, brings us, in a
very striking manner, to the passage from the physical to the
hyperphysical sciences.
We have seen already (chap. i.) that Galen and his predecessors had
satisfied themselves that the nerves are the channels of perception; a
doctrine which had been distinctly taught by Herophilus[61\17] in the
Alexandrian school. Herophilus, however, still combined, under the
common name of Nerves, the Tendons; though he distinguished such
Nerves from those which arise from the brain and the spinal marrow,
and which are subservient to the will. In Galen's time this subject
had been prosecuted more into detail. That anatomist has left a
Treatise expressly upon _The Anatomy of the Nerves_; in which he
describes the successive _Pairs_ of Nerves: thus, the First Pair are
the visual nerves: and we see, in the language which Galen uses, the
evidence of the care and interest with which he had himself examined
them. "These nerves," he says, "are not resolved into many fibres,
like all the other nerves, when they reach the organs to which they
belong; but spread out in a different and very remarkable manner,
which it is not easy to describe or to believe, without actually
seeing it." He then gives a description of the retina. In like manner
he describes the Second Pair, which is distributed to the muscles of
the eyes; the Third and Fourth Pairs, which go to the tongue and
palate; and so on to the Seventh Pair. This division into Seven Pairs
was established by Marinus,[62\17] but Vesalius found it to be
incomplete. The examination which is the basis of the anatomical
enumeration of the Nerves at present recognized was that of Willis.
His book, entitled _Cerebri Anatome, cui accessit Nervorum descriptio
et usus_, appeared at London in 1664. He made important additions to
the knowledge of this subject.[63\17] Thus he is the first who
describes in a distinct manner what has been called the _Nervous
Centre_,[64\17] the pyramidal eminences which, according to more
recent anatomists, are the communication of the brain with the spinal
marrow: and of which the _Decussation_, described by Santorini,
affords the explanation of the action of a part {463} of the brain
upon the nerves of the opposite side. Willis proved also that the
_Rete Mirabile_, the remarkable net-work of arteries at the base of
the brain, observed by the ancients in ruminating animals, does not
exist in man. He described the different Pairs of Nerves with more
care than his predecessors; and his mode of numbering them is employed
up to the present time. He calls the Olfactory Nerves the First Pair;
previously to him, these were not reckoned a Pair: and thus the optic
nerves were, as we have seen, called the first. He added the Sixth and
the Ninth Pairs, which the anatomists who preceded him did not reckon.
Willis also examined carefully the different _Ganglions_, or knots
which occur upon the nerves. He traced them wherever they were to be
found, and he gave a general figure of what Cuvier calls the _nervous
skeleton_, very superior to that of Vesalius, which was coarse and
inexact. Willis also made various efforts to show the connexion of the
parts of the brain. In the earlier periods of anatomy, the brain had
been examined by slicing it, so as to obtain a section. Varolius
endeavored to unravel it, and was followed by Willis. Vicq d'Azyr, in
modern times, has carried the method of section to greater perfection
than had before been given it;[65\17] as Vieussens and Gall have done
with respect to the method of Varolius and Willis. Recently Professor
Chaussier[66\17] makes three kinds of Nerves:--the _Encephalic_, which
proceed from the head, and are twelve on each side;--the _Rachidian_,
which proceed from the spinal marrow, and are thirty on each
side;--and _Compound Nerves_, among which is the _Great Sympathetic_
Nerve.
[Note 61\17: Spr. i. 534.]
[Note 62\17: _Dic. Sc. Med._ xxxv. 467.]
[Note 63\17: Cuv. _Sc. Nat._ p. 385.]
[Note 64\17: Ibid.]
[Note 65\17: Cuv. p. 40.]
[Note 66\17: _Dict. Sc. Nat._ xxxv. 467.]
One of the most important steps ever made in our knowledge of the
nerves is, the distinction which Bichat is supposed to have
established, of a _ganglionic system_, and a _cerebral system_. And
we may add, to the discoveries in nervous anatomy, the remarkable
one, made in our own time, that the two offices--of conducting the
motive impressions from the central seat of the will to the muscles,
and of propagating sensations from the surface of the body and the
external organs of sense to the sentient mind--reside in two
distinct portions of the nervous substance:--a discovery which has
been declared[67\17] to be "doubtless the most important accession
to physiological (anatomical) knowledge since the time of Harvey."
This doctrine was first published and taught by Sir Charles Bell:
after an interval of some {464} years, it was more distinctly
delivered in the publications of Mr. John Shaw, Sir C. Bell's pupil.
Soon afterwards it was further confirmed, and some part of the
evidence corrected, by Mr. Mayo, another pupil of Sir C. Bell, and
by M. Majendie.[68\17]
[Note 67\17: Dr. Charles Henry's _Report of Brit. Assoc._ iii.
p. 62.]
[Note 68\17: As authority for the expressions which I have now used
in the text, I will mention Müller's _Manual of Physiology_ (4th
edition, 1844). In Book iii. Section 2, Chap. i., "On the Nerves of
Sensation and Motion," Müller says, "Charles Bell was the first who
had the ingenious thought that the posterior roots of the nerves of
the spine--those which are furnished with a ganglion--govern
sensation only; that the anterior roots are appointed for motion;
and that the primitive fibres of these roots, after being united in
a single nervous cord, are mingled together in order to supply the
wants of the skin and muscles. He developed this idea in a little
work (_An Idea of a new Anatomy of the Brain_, London, 1811), which
was not intended to travel beyond the circle of his friends." Müller
goes on to say, that eleven years later, Majendie prosecuted the
same theory. But Mr. Alexander Shaw, in 1839, published _A Narrative
of the Discoveries of Sir Charles Bell in the Nervous System_, in
which it appears that Sir Charles Bell had further expounded his
views in his lectures to his pupils (p. 89), and that one of these,
Mr. John Shaw, had in various publications, in 1821 and 1822,
further insisted upon the same views; especially in a Memoir _On
Partial Paralysis_ (p. 75). MM. Mayo and Majendie both published
Memoirs in August, 1822; and these and subsequent works confirmed
the doctrine of Bell. Mr. Alexander Shaw states (p. 97), that a
mistake of Sir Charles Bell's, in an experiment which he had made to
prove his doctrine, was discovered through the joint labors of M.
Majendie and Mr. Mayo.]
_Sect._ 2.--_The Consequent Speculations. Hypotheses respecting
Life, Sensation, and Volition._
I SHALL not attempt to explain the details of these anatomical
investigations; and I shall speak very briefly of the speculations
which have been suggested by the obvious subservience of the nerves
to life, sensation, and volition. Some general inferences from their
distribution were sufficiently obvious; as, that the seat of
sensation and volition is in the brain. Galen begins his work, _On
the Anatomy of the Nerves_, thus: "That none of the members of the
animal either exercises voluntary motion, or receives sensation, and
that if the nerve be cut, the part immediately becomes inert and
insensible, is acknowledged by all physicians. But that the origin
of the nerves is partly from the brain, and partly from the spinal
marrow, I proceed to explain." And in his work _On the Doctrines of
Plato and Hippocrates_, he proves at {465} great length[69\17] that
the brain is the origin of sensation and motion, refuting the
opinions of earlier days, as that of Chrysippus,[70\17] who placed
the _hegemonic_ or master-principle of the soul, in the heart. But
though Galen thought that the rational soul resides in the brain, he
was disposed to agree with the poets and philosophers, according to
whom the heart is the seat of courage and anger, and the liver the
seat of love.[71\17] The faculties of the soul were by succeeding
physiologists confined to the brain; but the disposition still
showed itself, to attribute to them distinct localities. Thus
Willis[72\17] places the imagination in the _corpus callosum_, the
memory in the folds of the _hemispheres_, the perception in the
_corpus striatum_. In more recent times, a system founded upon a
similar view has been further developed by Gall and his followers.
The germ of Gall's system may be considered as contained in that of
Willis; for Gall represents the hemispheres as the folds of a great
membrane which is capable of being unwrapped and spread out, and
places the different faculties of man in the different regions of
this membrane. The chasm which intervenes between matter and motion
on the one side, and thought and feeling on the other, is brought
into view by all such systems; but none of the hypotheses which they
involve can effectually bridge it over.
[Note 69\17: Lib. vii.]
[Note 70\17: Lib. iii. c. 1.]
[Note 71\17: Lib. vi. c. 8.]
[Note 72\17: Cuv. _Sc. Nat._ p. 384.]
The same observation may be made respecting the attempts to explain
the manner in which the nerves operate as the instruments of
sensation and volition. Perhaps a real step was made by
Glisson,[73\17] professor of medicine in the University of
Cambridge, who distinguished in the fibres of the muscles of motion
a peculiar property, different from any merely mechanical or
physical action. His work _On the Nature of the Energetic Substance,
or on the Life of Nature and of its Three First Faculties, The
Perceptive, Appetitive, and Motive_, which was published in 1672, is
rather metaphysical than physiological. But the principles which he
establishes in this treatise he applies more specially to physiology
in a treatise _On the Stomach and Intestines_ (Amsterdam, 1677). In
this he ascribes to the fibres of the animal body a peculiar power
which he calls _Irritability_. He divides _irritation_ into natural,
vital, and animal; and he points out, though briefly, the gradual
differences of irritability in different organs. "It is hardly
comprehensible," says Sprengel,[74\17] "how this {466} lucid and
excellent notion of the Cambridge teacher was not accepted with
greater alacrity, and further unfolded by his contemporaries." It
has, however, since been universally adopted.
[Note 73\17: Cuv. _Sc. Nat._ p. 434.]
[Note 74\17: Spr. iv. 47.]
But though the discrimination of muscular irritability as a peculiar
power might be a useful step in physiological research, the
explanations hitherto offered, of the way in which the nerves
operate on this irritability, and discharge their other offices,
present only a series of hypotheses. Glisson[75\17] assumed the
existence of certain vital spirits, which, according to him, are a
mild, sweet fluid, resembling the spirituous part of white of egg,
and residing in the nerves.--This hypothesis, of a very subtle humor
or spirit existing in the nerves, was indeed very early taken
up.[76\17] This nervous spirit had been compared to air by
Erasistratus, Asclepiades, Galen, and others. The chemical
tendencies of the seventeenth century led to its being described as
acid, sulphureous or nitrous. At the end of that century, the
hypothesis of an _ether_ attracted much notice as a means of
accounting for many phenomena; and this ether was identified with
the nervous fluid. Newton himself inclines to this view, in the
remarkable Queries which are annexed to his _Opticks_. After
ascribing many physical effects to his ether, he adds (Query 23),
"Is not vision performed chiefly by the vibrations of this medium,
excited in the bottom of the eye by the rays of light, and
propagated through the solid, pellucid, and uniform capillamenta of
the nerves into the place of sensation?" And (Query 24), "Is not
animal motion performed by the vibrations of this medium, excited in
the brain by the power of the will, and propagated from thence
through the capillamenta of the nerves into the muscles for
contracting and dilating them?" And an opinion approaching this has
been adopted by some of the greatest of modern physiologists; as
Haller, who says,[77\17] that, though it is more easy to find what
this nervous spirit is not than what it is, he conceives that, while
it must be far too fine to be perceived by the sense, it must yet be
more gross than fire, magnetism, or electricity; so that it may be
contained in vessels, and confined by boundaries. And Cuvier speaks
to the same effect:[78\17] "There is a great probability that it is
by an imponderable fluid that the nerve acts on the fibre, and that
this nervous fluid is drawn from the blood, and secreted by the
medullary matter."
[Note 75\17: Spr. iv. 38.]
[Note 76\17: Haller, _Physiol._ iv. 365.]
[Note 77\17: _Physiol._ iv. 381, lib. x. sect. viii. § 15.]
[Note 78\17: _Règne Animal_, Introd. p. 30.]
Without presuming to dissent from such authorities on a point of
{467} anatomical probability, we may venture to observe, that these
hypotheses do not tend at all to elucidate the physiological
principle which is here involved; for this principle cannot be
mechanical, chemical, or physical, and therefore cannot be better
understood by embodying it in a fluid; the difficulty we have in
conceiving what the moving force _is_, is not got rid of by explaining
the machinery by which it is merely _transferred_. In tracing the
phenomena of sensation and volition to their cause, it is clear that
we must call in some peculiar and hyperphysical principle. The
hypothesis of a fluid is not made more satisfactory by attenuating
the fluid; it becomes subtle, spirituous, ethereal, imponderable, to
no purpose; it must cease to be a fluid, before its motions can
become sensation and volition. This, indeed, is acknowledged by most
physiologists; and strongly stated by Cuvier.[79\17] "The impression
of external objects upon the ME, the production of a sensation, of
an image, is a mystery impenetrable for our thoughts." And in
several places, by the use of this peculiar phrase, "_the me_," (_le
moi_) for the sentient and volent faculty, he marks, with peculiar
appropriateness and force, that phraseology borrowed from the world
of matter will, in this subject, no longer answer our purpose. We
have here to go from Nouns to Pronouns, from Things to Persons. We
pass from the Body to the Soul, from Physics to Metaphysics. We are
come to the borders of material philosophy; the next step is into
the domain of Thought and Mind. Here, therefore, we begin to feel
that we have reached the boundaries of our present subject. The
examination of that which lies beyond them must be reserved for a
philosophy of another kind, and for the labors of the future; if we
are ever enabled to make the attempt to extend into that loftier and
wider scene, the principles which we gather on the ground we are now
laboriously treading.
[Note 79\17: _Règne Animal_, Introd. p. 47.]
Such speculations as I have quoted respecting the nervous fluid,
proceeding from some of the greatest philosophers who ever lived,
prove only that hitherto the endeavor to comprehend the mystery of
perception and will, of life and thought, have been fruitless and
vain. Many anatomical truths have been discovered, but, so far as
our survey has yet gone, no genuine physiological principle. All the
trains of physiological research which we have followed have begun
in exact examination of organization and function, and have ended in
wide conjectures and arbitrary hypotheses. The stream of knowledge
in all such cases is {468} clear and lively at its outset; but,
instead of reaching the great ocean of the general truths of
science, it is gradually spread abroad among sands and deserts till
its course can be traced no longer.
Hitherto, therefore, we must consider that we have had to tell the
story of the _failures_ of physiological speculation. But of late
there have come into view and use among physiologists certain
principles which may be considered as peculiar to organized
subjects; and of which the introduction forms a real advance in
organical science. Though these have hitherto been very imperfectly
developed, we must endeavor to exhibit, in some measure, their
history and bearing.
[2nd Ed.] [In order to show that I am not unaware how imperfect the
sketch given in this work is, as a History of Physiology, I may
refer to the further discussions on these subjects contained in the
_Philosophy of the Inductive Sciences_, Book ix. I have there (Chap.
ii.) noticed the successive _Biological Hypotheses_ of the Mystical,
the Iatrochemical, and Iatromathematical Schools, the Vital-Fluid
School, and the Psychical School. I have (Chaps. iii., iv., v.)
examined several of the attempts which have been made to analyze the
Idea of Life, to classify Vital Functions, and to form Ideas of
Separate Vital Forces. I have considered in particular, the attempts
to form a distinct conception of Assimilation and Secretion, of
Generation, and of Voluntary Motion; and I have (Chap. vi.) further
discussed the Idea of Final Causes as employed in Biology.]
CHAPTER VI.
INTRODUCTION OF THE PRINCIPLE OF DEVELOPED AND METAMORPHOSED
SYMMETRY.
_Sect._ 1.--_Vegetable Morphology. Göthe. De Candolle._
BEFORE we proceed to consider the progress of principles which
belong to animal and human life, such as have just been pointed at,
we must look round for such doctrines, if any such there be, as
apply alike to all organized beings, conscious or unconscious, fixed
or locomotive;--to the laws which regulate vegetable as well as
animal forms and functions. Though we are very far from being able
to present a {469} clear and connected code of such laws, we may
refer to one law, at least, which appears to be of genuine authority
and validity; and which is worthy our attention as an example of a
properly organical or physiological principle, distinct from all
mechanical, chemical, or other physical forces; and such as cannot
even be conceived to be resolvable into those. I speak of the
tendency which produces such results as have been brought together
in recent speculations upon _Morphology_.
It may perhaps be regarded as indicating how peculiar are the
principles of organic life, and how far removed from any mere
mechanical action, that the leading idea in these speculations was
first strongly and effectively apprehended, not by a laborious
experimenter and reasoner, but by a man of singularly brilliant and
creative fancy; not by a mathematician or chemist, but by a poet.
And we may add further, that this poet had already shown himself
incapable of rightly apprehending the relation of physical facts to
their principles; and had, in trying his powers on such subjects,
exhibited a signal instance of the ineffectual and perverse
operation of the method of philosophizing to which the constitution
of his mind led him. The person of whom we speak, is John Wolfgang
Göthe, who is held, by the unanimous voice of Europe, to have been
one of the greatest poets of our own, or of any time, and whose
_Doctrine of Colors_ we have already had to describe, in the History
of Optics, as an entire failure. Yet his views on the laws which
connect the forms of plants into one simple system, have been
generally accepted and followed up. We might almost be led to think
that this writer's poetical endowments had contributed to this
scientific discovery;--the love of beauty of form, by fixing the
attention upon the symmetry of plants; and the creative habit of
thought, by making constant developement of a familiar
process.[80\17] {470}
[Note 80\17: We may quote some of the poet's own verses as an
illustration of his feelings on this subject. They are addressed to
a lady.
Dich verwirret, geliebte, die tausendfältige mischung
Dieses blumengewühls über dem garten umher;
Viele namen hörest du an, und immer verdränget,
Mit barbarischem klang, einer den andern im ohr.
Alle gestalten sind **ähnlich und keine gleichet der andern;
Und so deutet das chor auf ein geheimes gesetz,
Auf ein heiliges räthsel. O! könnte ich dich, liebliche freundinn,
Ueberliefern so gleich glücklich das lösende wort.
Thou, my love, art perplext with the endless seeming confusion
Of the luxuriant wealth which in the garden is spread;
Name upon name thou hearest, and in thy dissatisfied hearing,
With a barbarian noise one drives another along.
All the forms resemble, yet none is the same as another;
Thus the whole of the throng points at a deep hidden law.
Points at a sacred riddle. Oh! could I to thee, my beloved friend,
Whisper the fortunate word by which the riddle is read!]
But though we cannot but remark the peculiarity of our being
indebted to a poet for the discovery of a scientific principle, we
must not forget that he himself held, that in making this step, he
had been guided, not by his invention, but by observation. He
repelled, with extreme repugnance, the notion that he had
substituted fancy for fact, or imposed ideal laws on actual things.
While he was earnestly pursuing his morphological speculations, he
attempted to impress them upon Schiller. "I expounded to him, in as
lively a manner as possible, the metamorphosis of plants, drawing on
paper, with many characteristic strokes, a symbolic plant before his
eyes. He heard me," Göthe says,[81\17] "with much interest and
distinct comprehension; but when I had done, he shook his head, and
said, 'That is not Experience; that is an Idea:' I stopt with some
degree of irritation; for the point which separated us was marked
most luminously by this expression." And in the same work he relates
his botanical studies and his habit of observation, from which it is
easily seen that no common amount of knowledge and notice of
details, were involved in the course of thought which led him to the
principle of the Metamorphosis of Plants.
[Note 81\17:_ Zur Morphologie_, p. 24.]
Before I state the history of this principle, I may be allowed to
endeavor to communicate to the reader, to whom this subject is new,
some conception of the principle itself. This will not be difficult,
if he will imagine to himself a flower, for instance, a common
wild-rose, or the blossom of an apple-tree, as consisting of a
series of parts disposed in _whorls_, placed one over another on an
_axis_. The lowest whorl is the calyx with its five sepals; above
this is the corolla with its five petals; above this are a multitude
of stamens, which may be considered as separate whorls of five each,
often repeated; above these is a whorl composed of the ovaries, or
what become the seed-vessels in the fruit, which are five united
together in the apple, but indefinite in number and separate in the
rose. Now the morphological view is {471} this;--that the members of
each of these whorls are in their nature identical, and the same as
if they were whorls of ordinary leaves, brought together by the
shortening their common axis, and modified in form by the successive
elaboration of their nutriment. Further, according to this view, a
whorl of leaves itself is to be considered as identical with several
detached leaves dispersed spirally along the axis, and brought
together because the axis is shortened. Thus all the parts of a
plant are, or at least represent, the successive metamorphoses of
the same elementary member. The root-leaves thus pass into the
common leaves;--these into bracteæ;--these into the sepals;--these
into the petals;--these into the stamens with their anthers;--these
into the ovaries with their styles and stigmas;--these ultimately
become the fruit; and thus we are finally led to the seed of a new
plant.
Moreover the same notion of metamorphosis may be applied to explain
the existence of flowers which are not symmetrical like those we
have just referred to, but which have an irregular corolla or calyx.
The papilionaceous flower of the pea tribe, which is so markedly
irregular, may be deduced by easy gradations from the regular
flower, (through the _mimoseæ_,) by expanding one petal, joining one
or two others, and modifying the form of the intermediate ones.
Without attempting to go into detail respecting the proofs of that
identity of all the different organs, and all the different forms of
plants, which is thus asserted, we may observe, that it rests on
such grounds as these;--the transformations which the parts of
flowers undergo by accidents of nutriment or exposure. Such changes,
considered as monstrosities where they are very remarkable, show the
tendencies and possibilities belonging to the organization in which
they occur. For instance, the single wild-rose, by culture,
transforms many of its numerous stamens into petals, and thus
acquires the deeply folded flower of the double garden-rose. We
cannot doubt of the reality of this change, for we often see stamens
in which it is incomplete. In other cases we find petals becoming
leaves, and a branch growing out of the centre of the flower. Some
pear-trees, when in blossom, are remarkable for their tendencies to
such monstrosities.[82\17] Again, we find that flowers which are
usually irregular, occasionally become regular, and conversely. The
common snap-dragon (_Linaria vulgaris_) affords a curious instance
of this.[83\17] The usual form of this plant is "personate," the
corolla being divided into two lobes, which differ in form, and
{472} together present somewhat the appearance of an animal's face;
and the upper portion of the corolla is prolonged backwards into a
tube-like "spur." No flower can be more irregular; but there is a
singular variety of this plants termed _Peloria_, in which the
corolla is strictly symmetrical, consisting of a conical tube,
narrowed in front, elongated behind into five equal spurs, and
containing five stamens of equal length, instead of the two unequal
pairs of the didynamous Linaria. These and the like appearances show
that there is in nature a capacity for, and tendency to, such
changes as the doctrine of metamorphosis asserts.
[Note 82\17: Lindley, _Nat. Syst._ p. 84.]
[Note 83\17: Henslow, _Principles of Botany_, p. 116.]
Göthe's _Metamorphosis of Plants_ was published 1790: and his system
was the result of his own independent course of thoughts. The view
which it involved was not, however, absolutely new, though it had
never before been unfolded in so distinct and persuasive a manner.
Linnæus considered the leaves, calyx, corolla, stamens, each as
evolved in succession from the other; and spoke of it as _prolepsis_
or _anticipation_,[84\17] when the leaves changed accidentally into
bracteæ, these into a calyx, this into a corolla, the corolla into
stamens, or these into the pistil. And Caspar Wolf apprehended in a
more general manner the same principle. "In the whole plant," says
he,[85\17] "we see nothing but leaves and stalk;" and in order to
prove what is the situation of the leaves in all their later forms,
he adduces the cotyledons as the first leaves.
[Note 84\17: Sprengel, _Bot._ ii. 302. _Amœn. Acad._ vi. 324, 365.]
[Note 85\17: _Nov. Con. Ac. Petrop._ xii. 403, xiii. 478.]
Göthe was led to his system on this subject by his general views of
nature. He saw, he says,[86\17] that a whole life of talent and
labor was requisite to enable any one to arrange the infinitely
copious organic forms of a single kingdom of nature. "Yet I felt,"
he adds, "that for me there must be another way, analogous to the
rest of my habits. The appearance of the changes, round and round,
of organic creatures had taken strong hold on my mind. Imagination
and Nature appeared to me to vie with each other which could go on
most boldly yet most consistently." His observation of nature,
directed by such a thought, led him to the doctrine of the
metamorphosis.
[Note 86\17: _Zur Morph._ i. 30.]
In a later republication of his work (_Zur Morphologie_, 1817,) he
gives a very agreeable account of the various circumstances which
affected the reception and progress of his doctrine.
Willdenow[87\17] quoted {473} him thus:--"The life of plants is, as
Mr. Göthe very prettily says, an expansion and contraction, and
these alternations make the various periods of life." "This
'_prettily_,'" says Göthe, "I can be well content with, but the
'_egregie_,' of Usteri is much more pretty and obliging." Usteri had
used this term respecting Göthe in an edition of Jussieu.
[Note 87\17: _Zur Morph._ i. 121.]
The application of the notion of metamorphosis to the explanation of
double and monstrous flowers had been made previously by Jussieu.
Göthe's merit was, to have referred to it the _regular_ formation of
the flower. And as Sprengel justly says,[88\17] his view had so
profound a meaning, made so strong an appeal by its simplicity, and
was so fruitful in the most valuable consequences, that it was not
to be wondered at if it occasioned further examination of the
subject; although many persons pretend to slight it. The task of
confirming and verifying the doctrine by a general application of it
to all cases,--a labor so important and necessary after the
promulgation of any great principle,--Göthe himself did not execute.
At first he collected specimens and made drawings with some such
view,[89\17] but he was interrupted and diverted to other matters.
"And now," says he, in his later publication, "when I look back on
this undertaking, it is easy to see that the object which I had
before my eyes was, for me, in my position, with my habits and mode
of thinking, unattainable. For it was no less than this: that I was
to take that which I had stated in general, and presented to the
conception, to the mental intuition, in words; and that I should, in
a particularly visible, orderly, and gradual manner, present it to
the eye; so as to show to the outward sense that out of the germ of
this idea might grow a tree of physiology fit to overshadow the
world."
[Note 88\17: _Gesch. Botan._ ii. 304.]
[Note 89\17: _Zur Morph._ i. **129.]
Voigt, professor at Jena, was one of the first who adopted Göthe's
view into an elementary work, which he did in 1808. Other botanists
labored in the direction which had thus been pointed out. Of those
who have thus contributed to the establishment and developement of
the metamorphic doctrine. Professor De Candolle, of Geneva, is
perhaps the most important. His Theory of Developement rests upon
two main principles, _abortion_ and _adhesion_. By considering some
parts as degenerated or absent through the abortion of the buds
which might have formed them, and other parts as adhering together,
he holds that all plants may be reduced to perfect symmetry: and the
actual and constant occurrence of such incidents is shown beyond
{474} all doubt. And thus the snap-dragon, of which we have spoken
above, is derived from the Peloria, which is the normal condition of
the flower, by the abortion of one stamen, and the degeneration of
two others. Such examples are too numerous to need to be dwelt on.
_Sect._ 2.--_Application of Vegetable Morphology._
THE doctrine, being thus fully established, has been applied to
solve different problems in botany; for instance, to explain the
structure of flowers which appear at first sight to deviate widely
from the usual forms of the vegetable world. We have an instance of
such an application in Mr. Robert Brown's explanation of the real
structure of various plants which had been entirely misunderstood:
as, for example, the genus _Euphorbia_. In this plant he showed that
what had been held to be a jointed filament, was a pedicel with a
filament above it, the intermediate corolla having evanesced. In
_Orchideæ_ (the orchis tribe), he showed that the peculiar structure
of the plant arose from its having six stamens (two sets of three
each), of which five are usually abortive. In _Coniferæ_ (the
cone-bearing trees), it was made to appear that the seed was naked,
while the accompanying appendage, corresponding to a seed-vessel,
assumed all forms, from a complete leaf to a mere scale. In like
manner it was proved that the _pappus_, or down of _composite_
plants (as thistles), is a transformed calyx.
Along with this successful application of a profound principle, it
was natural that other botanists should make similar attempts. Thus
Mr. Lindley was led to take a view[90\17] of the structure of
_Reseda_ (mignonette) different from that usually entertained;
which, when published, attracted a good deal of attention, and
gained some converts among the botanists of Germany and France. But
in 1833, Mr. Lindley says, with great candor, "Lately, Professor
Henslow has satisfactorily proved, in part by the aid of a
monstrosity in the common _Mignonette_, in part by a severe
application of morphological rules, that my hypothesis must
necessarily be false." Such an agreement of different botanists
respecting the consequences of morphological rules, proves the
reality and universality of the rules.
[Note 90\17: Lindley, _Brit. Assoc. Report_, iii. 50.]
We find, therefore, that a principle which we may call the
_Principle of Developed and Metamorphosed Symmetry_, is firmly
established {475} and recognized, and familiarly and successfully
applied by botanists. And it will be apparent, on reflection, that
though _symmetry_ is a notion which applies to inorganic as well as
to organic things, and is, in fact, a conception of certain
relations of space and position, such _developement_ and
_metamorphosis_ as are here spoken of, are ideas entirely different
from any of those to which the physical sciences have led us in our
previous survey; and are, in short, genuine _organical_ or
_physiological_ ideas;--real elements of the philosophy of _life_.
We must, however imperfectly, endeavor to trace the application of
this idea in the other great department of the world of life; we
must follow the history of Animal Morphology.
CHAPTER VII.
PROGRESS OF ANIMAL MORPHOLOGY.
_Sect._ 1.--_Rise of Comparative Anatomy._
THE most general and constant relations of the form of the organs,
both in plants and animals, are the most natural grounds of
classification. Hence the first scientific classifications of
animals are the first steps in animal morphology. At first, a
_zoology_ was constructed by arranging animals, as plants were at
first arranged, according to their external parts. But in the course
of the researches of the anatomists of the seventeenth century, it
was seen that the internal structure of animals offered resemblances
and transitions of a far more coherent and philosophical kind, and
the Science of _Comparative Anatomy_ rose into favor and importance.
Among the main cultivators of this science[91\17] at the period just
mentioned, we find Francis Redi, of Arezzo; Guichard-Joseph
Duvernay, who was for sixty years Professor of Anatomy at the Jardin
du Roi at Paris, and during this lapse of time had for his pupils
almost all the greatest anatomists of the greater part of the
eighteenth century; Nehemiah Grew, secretary to the Royal Society of
London, whose _Anatomy of Plants_ we have already noticed.
[Note 91\17: Cuv. _Leçons sur l'Hist. des Sc. Nat._ 414, 420.]
But Comparative Anatomy, which had been cultivated with ardor {476}
to the end of the seventeenth century, was, in some measure,
neglected during the first two-thirds of the eighteenth. The
progress of botany was, Cuvier sagaciously suggests,[92\17] one
cause of this; for that science had made its advances by confining
itself to external characters, and rejecting anatomy; and though
Linnæus acknowledged the dependence of zoology upon anatomy[93\17]
so far as to make the number of teeth his characters, even this was
felt, in his method, as a bold step. But his influence was soon
opposed by that of Buffon, Daubenton, and Pallas; who again brought
into view the importance of comparative anatomy in Zoology; at the
same time that Haller proved how much might be learnt from it in
Physiology. John Hunter in England, the two Monros in Scotland,
Camper in Holland, and Vicq d'Azyr in France, were the first to
follow the path thus pointed out. Camper threw the glance of genius
on a host of interesting objects, but almost all that he produced
was a number of sketches; Vicq d'Azyr, more assiduous, was stopt in
the midst of a most brilliant career by a premature death.
[Note 92\17: Cuv. _Hist. Sc. Nat._ i. 301.]
[Note 93\17: Ib.]
Such is Cuvier's outline of the earlier history of comparative
anatomy. We shall not go into detail upon this subject; but we may
observe that such studies had fixed in the minds of naturalists the
conviction of the possibility and the propriety of considering large
divisions of the animal kingdom as modifications of one common
_type_. Belon, as early as 1555, had placed the skeleton of a man
and a bird side by side, and shown the correspondence of parts. So
far as the case of vertebrated animals extends, this correspondence
is generally allowed; although it required some ingenuity to detect
its details in some cases; for instance, to see the analogy of parts
between the head of a man and a fish.
In tracing these less obvious correspondencies, some curious steps
have been made in recent times. And here we must, I conceive, again
ascribe no small merit to the same remarkable man who, as we have
already had to point out, gave so great an impulse to vegetable
morphology. Göthe, whose talent and disposition for speculating on
all parts of nature were truly admirable, was excited to the study
of anatomy by his propinquity to the Duke of Weimar's cabinet of
natural history. In 1786, he published a little essay, the object of
which was to show that in man, as well as in beasts, the upper jaw
contains an intermaxillary bone, although the sutures are
obliterated. After 1790,[94\17] animated and impelled by the same
passion for natural {477} observation and for general views, which
had produced his Metamorphosis of Plants, he pursued his
speculations on these subjects eagerly and successfully. And in
1795, he published a _Sketch of a Universal Introduction into
Comparative Anatomy, beginning with Osteology_; in which he attempts
to establish an "osteological type," to which skeletons of all
animals may be referred. I do not pretend that Göthe's anatomical
works have had any influence on the progress of the science
comparable with that which has been exercised by the labors of
professional anatomists; but the ingenuity and value of the views
which they contained was acknowledged by the best authorities; and
the clearer introduction and application of the principle of
developed and metamorphosed symmetry may be dated from about this
time. Göthe declares that, at an early period of these speculations,
he was convinced[95\17] that the bony head of beasts is to be
derived from six vertebræ. In 1807, Oken published a "Program" _On
the Signification of the Bones of the Skull_, in which he maintained
that these bones are equivalent to four vertebræ); and Meckel, in
his _Comparative Anatomy_, in 1811, also resolved the skull into
vertebræ. But Spix, in his elaborate work _Cephalogenesis_, in 1815,
reduced the vertebræ of the head to three. "Oken," he says,[96\17]
"published opinions merely theoretical, and consequently contrary to
those maintained in this work, which are drawn from observation."
This resolution of the head into vertebræ is assented to by many of
the best physiologists, as explaining the distribution of the
nerves, and other phenomena. Spix further extended the application
of the vertebral theory to the heads of all classes of vertebrate
animals; and Bojanus published a Memoir expressly on the vertebral
structure of the skulls of fishes in Oken's _Isis_ for 1818.
Geoffroy Saint-Hilaire presented a lithographic plate to the French
Academy in February 1824, entitled _Composition de la Tête **osseuse
chez l'Homme et les Animaux_, and developed his views of the
vertebral composition of the skull in two Memoirs published in the
_Annales des Sciences Naturelles_ for 1824. We cannot fail to
recognize here the attempt to apply to the skeleton of animals the
principle which leads botanists to consider all the parts of a
flower as transformations of the same organs. How far the
application of the principle, as here proposed, is just, I must
leave philosophical physiologists to decide.
[Note 94\17: _Zur Morphologie_, i. 234.]
[Note 95\17: _Zur Morphologie_, 250.]
[Note 96\17: Spix, _Cephalogenesis_.]
By these and similar researches, it is held by the best
physiologists {478} that the skull of all vertebrate animals is
pretty well reduced to a uniform structure, and the laws of its
variations nearly determined.[97\17]
[Note 97\17: Cuv. _Hist. Sc. Nat._ iii. 442.]
The vertebrate animals being thus reduced to a single type, the
question arises how far this can be done with regard to other
animals, and how many such types there are. And here we come to one
of the important services which Cuvier rendered to natural history.
_Sect._ 2.--_Distinction of the General Types of the Forms of
Animals.--Cuvier._
ANIMALS were divided by Lamarck into vertebrate and invertebrate;
and the general analogies of all vertebrate animals are easily made
manifest. But with regard to other animals, the point is far from
clear. Cuvier was the first to give a really philosophical view of
the animal world in reference to the plan on which each animal is
constructed. There are,[98\17] he says, four such plans;--four forms
on which animals appear to have been modelled; and of which the
ulterior divisions, with whatever titles naturalists have decorated
them, are only very slight modifications, founded on the development
or addition of some parts which do not produce any essential change
in the plan.
[Note 98\17: _Règne Animal_, p. 57.]
These four great branches of the animal world are the _vertebrata_,
_mollusca_, _articulata_, _radiata_; and the differences of these
are so important that a slight explanation of them may be permitted.
The _vertebrata_ are those animals which (as man and other sucklers,
birds, fishes, lizards, frogs, serpents) have a backbone and a skull
with lateral appendages, within which the viscera are included, and
to which the muscles are attached.
The _mollusca_, or soft animals, have no bony skeleton; the muscles
are attached to the skin, which often includes stony plates called
_shells_; such molluscs are shell-fish; others are cuttle-fish, and
many pulpy sea-animals.
The _articulata_ consist of _crustacea_ (lobsters, &c.), _insects_,
_spiders_, and _annulose worms_, which consist of a head and a
number of successive annular portions of the body _jointed_ together
(to the interior of which the muscles are attached), whence the name.
Finally, the _radiata_ include the animals known under the name of
_zoophytes_. In the preceding three branches the organs of motion
and of sense were distributed symmetrically on the two sides of an
axis, {479} so that the animal has a right and a left side. In the
radiata the similar members radiate from the axis in a circular
manner, like the petals of a regular flower.
The whole value of such a classification cannot be understood
without explaining its use in enabling us to give general
descriptions, and general laws of the animal functions of the
classes which it includes; but in the present part of our work our
business is to exhibit it as an exemplification of the reduction of
animals to laws of Symmetry. The bipartite Symmetry of the form of
vertebrate and articulate animals is obvious; and the reduction of
the various forms of such animals to a common type has been
effected, by attention to their anatomy, in a manner which has
satisfied those who have best studied the subject. The molluscs,
especially those in which the head disappears, as oysters, or those
which are rolled into a spiral, as snails, have a less obvious
Symmetry, but here also we can apply certain general types. And the
Symmetry of the radiated zoophytes is of a nature quite different
from all the rest, and approaching, as we have suggested, to the
kind of Symmetry found in plants. Some naturalists have doubted
whether[99\17] these zoophytes are not referrible to two types
(_acrita_ or polypes, and true _radiata_,) rather than to one.
[Note 99\17: _Brit. Assoc. Rep._ iv. 227.]
This fourfold division was introduced by Cuvier.[100\17] Before him,
naturalists followed Linnæus, and divided non-vertebrate animals
into two classes, insects and worms. "I began," says Cuvier, "to
attack this view of the subject, and offered another division, in a
Memoir read at the Society of Natural History of Paris, the 21st of
Floreal, in the year III. of the Republic (May 10, 1795,) printed in
the _Décade Philosophique_: in this, I mark the characters and the
limits of molluscs, insects, worms, echinoderms, and zoophytes. I
distinguish the red-blooded worms or annelides, in a Memoir read to
the Institute, the 11th Nivose, year X. (December 31, 1801.) I
afterwards distributed these different classes into three branches,
each co-ordinate to the branch formed by the vertebrate animals, in
a Memoir read to the Institute in July, 1812, printed in the
_Annales du Muséum d'Histoire Naturelle_, tom. xix." His great
systematic work, the _Règne Animal_, founded on this distribution,
was published in 1817; and since that time the division has been
commonly accepted among naturalists.
[Note 100\17: _Règne A._ 61.]
[2nd Ed.] [The question of the Classification of Animals is
discussed in the first of Prof. Owen's _Lectures on the
Invertebrate_ {480} _Animals_ (1843). Mr. Owen observes that the
arrangement of animals into _Vertebrate_ and _Invertebrate_ which
prevailed before Cuvier, was necessarily bad, inasmuch as no
_negative_ character in Zoology gives true natural groups. Hence the
establishment of the _sub-kingdoms_, _Mollusca_, _Articulata_,
_Radiata_, as co-ordinate with _Vertebrata_, according to the
arrangement of the nervous system, was a most important advance. But
Mr. Owen has seen reason to separate the _Radiata_ of Cuvier into
two divisions; the _Nematoneura_, in which the nervous system can be
traced in a filamentary form (including _Echinoderma_,
_Ciliobrachiata_, _Cœlelmintha_, _Rotifera_,) and the _Acrita_ or
lowest division of the animal kingdom, including _Acalepha_,
_Nudibrachiata_, _Sterelmintha_, _Polygastria_.]
_Sect._ 3.--_Attempts to establish the Identity of the Types of
Animal Forms._
SUPPOSING this great step in Zoology, of which we have given an
account,--the reduction of all animals to four types or plans,--to
be quite secure, we are then led to ask whether any further advance
is possible;--whether several of these types can be referred to one
common form by any wider effort of generalization. On this question
there has been a considerable difference of opinion. Geoffroy
Saint-Hilaire,[101\17] who had previously endeavored to show that
all vertebrate animals were constructed so exactly upon the same
plan as to preserve the strictest analogy of parts in respect to
their osteology, thought to extend this unity of plan by
demonstrating, that the hard parts of crustaceans and insects are
still only modifications of the skeleton of higher animals, and that
therefore the type of vertebrata must be made to include them
also:--the segments of the articulata are held to be strictly
analogous to the vertebras of the higher animals, and thus the
former live _within_ their vertebral column in the same manner as
the latter live _without_ it. Attempts have even been made to reduce
molluscous and vertebrate animals to a community of type, as we
shall see shortly.
[Note 101\17: Mr. Jenyns, _Brit. Assoc. Rep._ iv. 150.]
Another application of the principle, according to which creatures
the most different are developments of the same original type, may
be discerned[102\17] in the doctrine, that the embryo of the higher
forms of animal life passes by gradations through those forms which
are {481} permanent in inferior animals. Thus, according to this
view, the human fœtus assumes successively the plan of the zoophyte,
the worm, the fish, the turtle, the bird, the beast. But it has been
well observed, that "in these analogies we look in vain for the
precision which can alone support the inference that has been
deduced;"[103\17] and that at each step, the higher embryo and the
lower animal which it is supposed to resemble, differ in having each
different organs suited to their respective destinations.
[Note 102\17: Dr. Clark, _Report_, Ib. iv. 113.]
[Note 103\17: Dr. Clark, p. 114.]
Cuvier[104\17] never assented to this view, nor to the attempts to
refer the different divisions of his system to a common type. "He
could not admit," says his biographer, "that the lungs or gills of
the vertebrates are in the same connexion as the branchiæ of
molluscs and crustaceans, which in the one are situated at the base
of the feet, or fixed on the feet themselves, and in the other often
on the back or about the arms. He did not admit the analogy between
the skeleton of the vertebrates and the skin of the articulates; he
could not believe that the tænia and the sepia were constructed on
the same plan; that there was a similarity of composition between
the bird and the echinus, the whale and the snail; in spite of the
skill with which some persons sought gradually to efface their
discrepancies."
[Note 104\17: Laurillard, _Elog. de Cuvier_, p. 66.]
Whether it may be possible to establish, among the four great
divisions of the "Animal Kingdom," some analogies of a higher order
than those which prevail within each division, I do not pretend to
conjecture. If this can be done, it is clear that it must be by
comparing the types of these divisions under their most general
forms: and thus Cuvier's arrangement, so far as it is itself rightly
founded on the unity of composition of each branch, is the surest
step to the discovery of a unity pervading and uniting these
branches. But those who generalize surely, and those who generalize
rapidly, may travel in the same direction, they soon separate so
widely, that they appear to move from each other. The partisans of a
universal "unity of composition" of animals, accused Cuvier of being
too inert in following the progress of physiological and zoological
science. Borrowing their illustration from the political parties of
the times, they asserted that he belonged to the science of
_resistance_, not to the science of the _movement_. Such a charge
was highly honorable to him; for no one acquainted with the history
of zoology can doubt that he had a great share in the impulse by
which the "movement" was occasioned; or that he {482} himself made a
large advance with it; and it was because he was so poised by the
vast mass of his knowledge, so temperate in his love of doubtful
generalizations, that he was not swept on in the wilder part of the
stream. To such a charge, moderate reformers, who appreciate the
value of the good which exists, though they try to make it better,
and who know the knowledge, thoughtfulness, and caution, which are
needful in such a task, are naturally exposed. For us, who can only
decide on such a subject by the general analogies of the history of
science, it may suffice to say, that it appears doubtful whether the
fundamental conceptions of affinity, analogy, transition, and
developement, have yet been fixed in the minds of physiologists with
sufficient firmness and clearness, or unfolded with sufficient
consistency and generality, to make it likely that any great
additional step of this kind can for some time be made.
We have here considered the doctrine of the identity of the
seemingly various types of animal structure, as an attempt to extend
the correspondencies which were the basis of Cuvier's division of
the animal kingdom. But this doctrine has been put forward in
another point of view, as the antithesis to the doctrine of final
causes. This question is so important a one, that we cannot help
attempting to give some view of its state and bearings.
CHAPTER VIII.
THE DOCTRINE OF FINAL CAUSES IN PHYSIOLOGY.
_Sect._ 1.--_Assertion of the Principle of Unity of Plan._
WE have repeatedly seen, in the course of our historical view of
Physiology, that those who have studied the structure of animals and
plants, have had a conviction forced upon them, that the organs are
constructed and combined in subservience to the life and functions
of the whole. The parts have a _purpose_, as well as a _law_;--we
can trace Final Causes, as well as Laws of Causation. This principle
is peculiar to physiology; and it might naturally be expected that,
in the progress of the science, it would come under special
consideration. This accordingly has happened; and the principle has
been drawn {483} into a prominent position by the struggle of two
antagonistic schools of physiologists. On the one hand, it has been
maintained that this doctrine of final causes is altogether
unphilosophical, and requires to be replaced by a more comprehensive
and profound principle: on the other hand, it is asserted that the
doctrine is not only true, but that, in our own time, it has been
fixed and developed so as to become the instrument of some of the
most important discoveries which have been made. Of the views of
these two schools we must endeavor to give some account.
The disciples of the former of the two schools express their tenets
by the phrases _unity_ of _plan_, _unity_ of _composition_; and the
more detailed developement of these doctrines has been termed the
_Theory of Analogies_, by Geoffroy Saint-Hilaire, who claims this
theory as his own creation. According to this theory, the structure
and functions of animals are to be studied by the guidance of their
analogy only; our attention is to be turned, not to the fitness of
the organization for any end of life or action, but to its
resemblance to other organizations by which it is gradually derived
from the original type.
According to the rival view of this subject, we must not assume, and
cannot establish, that the plan of all animals is the same, or their
composition similar. The existence of a single and universal system
of analogies in the construction of all animals is entirely
unproved, and therefore cannot be made our guide in the study of
their properties. On the other hand, the plan of the animal, the
purpose of its organization in the support of its life, the
necessity of the functions to its existence, are truths which are
irresistibly apparent, and which may therefore be safely taken as
the bases of our reasonings. This view has been put forward as the
doctrine of the _conditions of existence_: it may also be described
as the principle of _a purpose in organization_; the structure being
considered as having the function for its end. We must say a few
words on each of these views.
It had been pointed out by Cuvier, as we have seen in the last
chapter, that the animal kingdom may be divided into four great
branches; in each of which the _plan_ of the animal is different,
namely, _vertebrata_, _articulata_, _mollusca_, _radiata_. Now the
question naturally occurs, is there really no resemblance of
construction in these different classes? It was maintained by some,
that there is such a resemblance. In 1820,[105\17] M. Audouin, a
young naturalist of Paris, {484} endeavored to fill up the chasm
which separates insects from other animals; and by examining
carefully the portions which compose the solid frame-work of
insects, and following them through their various transformations in
different classes, he conceived that he found relations of position
and function, and often of number and form, which might be compared
with the relations of the parts of the skeleton in vertebrate
animals. He thought that the first segment of an insect, the
head,[106\17] represents one of the three vertebræ which, according
to Spix and others, compose the vertebrate head: the second segment
of the insects, (the _prothorax_ of Audouin,) is, according to M.
Geoffroy, the second vertebra of the head of the vertebrata, and so
on. Upon this speculation Cuvier[107\17] does not give any decided
opinion; observing only, that even if false, it leads to active
thought and useful research.
[Note 105\17: Cuv. _Hist. Sc. Nat._ iii. 422.]
[Note 106\17: Ib. 437.]
[Note 107\17: Cuv. _Hist. Sc. Nat._ iii. 441.]
But when an attempt was further made to identify the plan of another
branch of the animal world, the mollusca, with that of the
vertebrata, the radical opposition between such views and those of
Cuvier, broke out into an animated controversy.
Two French anatomists, MM. Laurencet and Meyranx, presented to the
Academy of Sciences, in 1830, a Memoir containing their views on the
organization of molluscous animals; and on the sepia or cuttle-fish
in particular, as one of the most complete examples of such animals.
These creatures, indeed, though thus placed in the same division
with shell-fish of the most defective organization and obscure
structure, are far from being scantily organized. They have a
brain,[108\17] often eyes, and these, in the animals of this class,
(_cephalopoda_) are more complicated than in any
vertebrates;[109\17] they have sometimes ears, salivary glands,
multiple stomachs, a considerable liver, a bile, a complete double
circulation, provided with auricles and ventricles; in short, their
vital activity is vigorous, and their senses are distinct.
[Note 108\17: Geoffroy Saint-Hilaire denies this. _Principes de
Phil. Zoologique discutés en_ 1830, p. 68.]
[Note 109\17: Geoffroy Saint-Hilaire, _Principes de Phil. Zoologique
discutés en_ 1830, p. 55.]
But still, though this organization, in the abundance and diversity
of its parts, approaches that of vertebrate animals, it had not been
considered as composed in the same manner, or arranged in the same
order, Cuvier had always maintained that the plan of molluscs is not
a continuation of the plan of vertebrates. {485}
MM. Laurencet and Meyranx, on the contrary, conceived that the sepia
might be reduced to the type of a vertebrate creature, by
considering the back-bone of the latter bent double backwards, so as
to bring the root of the tail to the nape of the neck; the parts
thus brought into contact being supposed to coalesce. By this mode
of conception, these anatomists held that the viscera were placed in
the same connexion as in the vertebrate type, and the functions
exercised in an analogous manner.
To decide on the reality of the analogy thus asserted, clearly
belonged to the jurisdiction of the most eminent anatomists and
physiologists. The Memoir was committed to Geoffroy Saint-Hilaire
and Latreille, two eminent zoologists, in order to be reported on.
Their report was extremely favorable; and went almost to the length
of adopting the views of the authors.
Cuvier expressed some dissatisfaction with this report on its being
read;[110\17] and a short time afterwards,[111\17] represented
Geoffroy Saint-Hilaire as having asserted that the new views of
Laurencet and Meyranx refuted completely the notion of the great
interval which exists between molluscous and vertebrate animals.
Geoffroy protested against such an interpretation of his
expressions; but it soon appeared, by the controversial character
which the discussions on this and several other subjects assumed,
that a real opposition of opinions was in action.
[Note 110\17: _Princ. de Phil. Zool. discutés en_ 1830, p. 36.]
[Note 111\17: p. 50.]
Without attempting to explain the exact views of Geoffroy, (we may,
perhaps, venture to say that they are hardly yet generally
understood with sufficient distinctness to justify the mere
historian of science in attempting such an explanation,) their
general tendency may be sufficiently collected from what has been
said; and from the phrases in which his views are conveyed.[112\17]
_The principle of connexions, the elective affinities of organic
elements, the equilibrization of organs_;--such are the designations
of the leading doctrines which are unfolded in the preliminary
discourse of his _Anatomical Philosophy_. Elective affinities of
organic elements are the forces by which the vital structures and
varied forms of living things are produced; and the principles of
connexion and equilibrium of these forces in the various parts of
the organization prescribe limits and conditions to the variety and
developement of such forms.
[Note 112\17: _Phil. Zool._ 15.]
The character and tendency of this philosophy will be, I think,
{486} much more clear, if we consider what it excludes and denies.
It rejects altogether all conception of a plan and purpose in the
organs of animals, as a principle which has determined their forms,
or can be of use in directing our reasonings. "I take care," says
Geoffroy, "not to ascribe to God any intention."[113\17] And when
Cuvier speaks of the combination of organs in such order that they
may be in consistence with the part which the animal _has to play_
in nature; his rival rejoins,[114\17] I "know nothing of animals
which _have to play_ a part in nature." Such a notion is, he holds,
unphilosophical and dangerous. It is an abuse of final causes which
makes the cause to be engendered by the effect. And to illustrate
still further his own view, he says, "I have read concerning
fishes, that because they live in a medium which resists more than
air, their motive forces are calculated so as to give them the power
of progression under those circumstances. By this mode of reasoning,
you would say of a man who makes use of crutches, that he was
originally destined to the misfortune of having a leg paralysed or
amputated."
[Note 113\17: "Je me garde de prêter à Dieu aucune intention."
_Phil. Zool._ 10.]
[Note 114\17: "Je ne connais point d'animal qui DOIVE jouer un rôle
dans la nature." p. 65.]
How far this doctrine of unity in the plan in animals, is admissible
or probable in physiology when kept within proper limits, that is,
when not put in opposition to the doctrine of a purpose involved in
the plan of animals, I do not pretend even to conjecture. The
question is one which appears to be at present deeply occupying the
minds of the most learned and profound physiologists; and such
persons alone, adding to their knowledge and zeal, judicial sagacity
and impartiality, can tell us what is the general tendency of the
best researches on this subject.[115\17] But when the anatomist
expresses such opinions, and defends them by such illustrations as
those which I have just quoted,[116\17] we perceive that he quits
the entrenchments of his superior science, in which he might {487}
have remained unassailable so long as the question was a
professional one; and the discussion is open to those who possess no
peculiar knowledge of anatomy. We shall, therefore, venture to say a
few words upon it.
[Note 115\17: So far as this doctrine is generally accepted among
the best physiologists, we cannot doubt the propriety of Meckel's
remark, (_Comparative Anatomy_, 1821, Pref. p. xi.) that it cannot
be truly asserted either to be new, or to be peculiarly due to
Geoffroy Saint-Hilaire.]
[Note 116\17: It is hardly worth while answering such illustrations,
but I may remark, that the one quoted above, irrelevant and
unbecoming as it is, tells altogether against its author. The fact
that the wooden leg is of the same length as the other, proves, and
would satisfy the most incredulous man, that it was _intended_ for
walking.]
_Sect._ 2.--_Estimate of the Doctrine of Unity of Plan._
IT has been so often repeated, and so generally allowed in modern
times, that Final Causes ought not to be made our guides in natural
philosophy, that a prejudice has been established against the
introduction of any views to which this designation can be applied,
into physical speculations. Yet, in fact, the assumption of an end
or purpose in the structure of organized beings, appears to be an
intellectual habit which no efforts can cast off. It has prevailed
from the earliest to the latest ages of zoological research; appears
to be fastened upon us alike by our ignorance and our knowledge; and
has been formally accepted by so many great anatomists, that we
cannot feel any scruple in believing the rejection of it to be the
superstition of a false philosophy, and a result of the exaggeration
of other principles which are supposed capable of superseding its
use. And the doctrine of unity of plan of all animals, and the other
principles associated with this doctrine, so far as they exclude the
conviction of an intelligible scheme and a discoverable end, in the
organization of animals, appear to be utterly erroneous. I will
offer a few reasons for an opinion which may appear presumptuous in
a writer who has only a general knowledge of the subject.
1. In the first place, it appears to me that the argumentation on
the case in question, the Sepia, does by no means turn out to the
advantage of the new hypothesis. The arguments in support of the
hypothetical view of the structure of this mollusc were, that by
this view the relative position of the parts was explained, and
confirmations which had appeared altogether anomalous, were reduced
to rule; for example, the beak, which had been supposed to be in a
position the reverse of all other beaks, was shown, by the assumed
posture, to have its upper mandible longer than the lower, and thus
to be regularly placed. "But," says Cuvier,[117\17] "supposing the
posture, in order that the side on which the funnel of the sepia is
folded should be the back of the animal, considered as similar to a
vertebrate, the brain with {488} regard to the beak, and the
œsophagus with regard to the liver, should have positions
corresponding to those in vertebrates; but the positions of these
organs are exactly contrary to the hypothesis. How, then, can you
say," he asks, "that the cephalopods and vertebrates have _identity
of composition_, _unity of composition_, without using words in a
sense entirely different from their common meaning?"
[Note 117\17: _G. S. H. Phil. Zool._ p. 70.]
This argument appears to be exactly of the kind on which the value
of the hypothesis must depend.[118\17] It is, therefore, interesting
to see the reply made to it by the theorist. It is this: "I admit
the facts here stated, but I deny that they lead to the notion of a
different sort of animal composition. Molluscous animals had been
placed too high in the zoological scale; but if they are only the
embryos of its lower stages, if they are only beings in which far
fewer organs come into play, it does not follow that the organs are
destitute of the relations which the power of successive generations
may demand. The organ A will be in an unusual relation with the
organ C, if B has not been produced;--if a stoppage of the
developement has fallen upon this latter organ, and has thus
prevented its production. And thus," he says, "we see how we may
have different arrangements, and divers constructions as they appear
to the eye."
[Note 118\17: I do not dwell on other arguments which were employed.
It was given as a circumstance suggesting the supposed posture of
the type, that in this way the back was colored, and the belly was
white. On this Cuvier observes (_Phil. Zool._ pp. 93, 68), "I must
say, that I do not know any naturalist so ignorant as to suppose
that the back is determined by its dark color, or even by its
position when the animal is in motion; they all know that the badger
has a black belly and a white back; that an infinity of other
animals, especially among insects, are in the same case; and that
many fishes swim on their side, or with their belly upwards."]
It seems to me that such a concession as this entirely destroys the
theory which it attempts to defend; for what arrangement does the
principle of unity of composition _exclude_, if it admits unusual,
that is, various arrangements of some organs, accompanied by the
total absence of others? Or how does this differ from Cuvier's mode
of stating the conclusion, except in the introduction of certain
arbitrary hypotheses of developement and stoppage? "I reduce the
facts," Cuvier says, "to their true expression, by saying that
Cephalopods have several organs which are common to them and
vertebrates, and which discharge the same offices; but that these
organs are in them differently distributed, and often constructed in
a different manner; {489} and they are accompanied by several other
organs which vertebrates have not; while these on the other hand
have several which are wanting in cephalopods."
We shall see afterwards the general principles which Cuvier himself
considered as the best guides in these reasonings. But I will first
add a few words on the disposition of the school now under
consideration, to reject all assumption of an end.
2. That the parts of the bodies of animals are made in order to
discharge their respective offices, is a conviction which we cannot
believe to be otherwise than an irremovable principle of the
philosophy of organization, when we see the manner in which it has
constantly forced itself upon the minds of zoologists and anatomists
in all ages; not only as an inference, but as a guide whose
indications they could not help following. I have already noticed
expressions of this conviction in some of the principal persons who
occur in the history of physiology, as Galen and Harvey. I might add
many more, but I will content myself with adducing a contemporary of
Geoffroy's whose testimony is the more remarkable, because he
obviously shares with his countryman in the common prejudice against
the use of final causes. "I consider," he says, in speaking of the
provisions for the reproduction of animals,[119\17] "with the great
Bacon, the philosophy of final causes as sterile; but I have
elsewhere acknowledged that it was very difficult for the most
cautious man never to have recourse to them in his explanations."
After the survey which we have had to take of the history of
physiology, we cannot but see that the assumption of final causes in
this branch of science is so far from being sterile, that it has had
a large share in every discovery which is included in the existing
mass of real knowledge. The use of every organ has been discovered
by starting from the assumption that it must have _some_ use. The
doctrine of the circulation of the blood was, as we have seen,
clearly and professedly due to the persuasion of a purpose in the
circulatory apparatus. The study of comparative anatomy is the study
of the adaption of animal structures to their purposes. And we shall
soon have to show that this conception of final causes has, in our
own times, been so far from barren, that it has, in the hands of
Cuvier and others, enabled us to become intimately acquainted with
vast departments of zoology to which we have no other mode of
access. It has placed before us in a complete state, {490} animals,
of which, for thousands of years, only a few fragments have existed,
and which differ widely from all existing animals; and it has given
birth, or at least has given the greatest part of its importance and
interest, to a science which forms one of the brightest parts of the
modern progress of knowledge. It is, therefore, very far from being
a vague and empty assertion, when we say that final causes are a
real and indestructible element in zoological philosophy; and that
the exclusion of them, as attempted by the school of which we speak,
is a fundamental and most mischievous error.
[Note 119\17: Cabanis, _Rapports du Physique et du Morale de
l'Homme_, i. **299.]
3. Thus, though the physiologist may persuade himself that he ought
not to refer to final causes, we find that, practically, he cannot
help doing this; and that the event shows that his practical habit
is right and well-founded. But he may still cling to the speculative
difficulties and doubts in which such subjects may be involved by _à
priori_ considerations. He may say, as Saint-Hilaire does
say,[120\17] "I ascribe no intention to God, for I mistrust the
feeble powers of my reason. I observe facts merely, and go no
further. I only pretend to the character of the historian of _what
is_." "I cannot make Nature an intelligent being who does nothing in
vain, who acts by the shortest mode, who does all for the best."
[Note 120\17: _Phil. Zool._ p. 10.]
I am not going to enter at any length into this subject, which, thus
considered, is metaphysical and theological, rather than
physiological. If any one maintain, as some have maintained, that no
manifestation of means apparently used for ends in nature, can prove
the existence of design in the Author of nature, this is not the
place to refute such an opinion in its general form. But I think it
may be worth while to show, that even those who incline to such an
opinion, still cannot resist the necessity which compels men to
assume, in organized beings, the existence of an end.
Among the philosophers who have referred our conviction of the being
of God to our moral nature, and have denied the possibility of
demonstration on mere physical grounds, Kant is perhaps the most
eminent. Yet he has asserted the reality of such a principle of
physiology as we are now maintaining in the most emphatic manner.
Indeed, this assumption of an end makes his very definition of an
organized being. "An organized product of nature is that in which
all the parts are mutually ends and means."[121\17] And this, he
says, is a universal and necessary maxim. He adds, "It is well known
that the {491} anatomizers of plants and animals, in order to
investigate their structure, and to obtain an insight into the
grounds why and to what end such parts, why such a situation and
connexion of the parts, and exactly such an internal form, come
before them, assume, as indispensably necessary, this maxim, that in
such a creature nothing is _in vain_, and proceed upon it in the
same way in which in general natural philosophy we proceed upon the
principle that _nothing happens by chance_. In fact, they can as
little free themselves from this _teleological_ principle as from
the general physical one; for as, on omitting the latter, no
experience would be possible, so on omitting the former principle,
no clue could exist for the observation of a kind of natural objects
which can be considered teleologically under the conception of
natural ends."
[Note 121\17: _Urtheilskraft_, p. 296.]
Even if the reader should not follow the reasoning of this
celebrated philosopher, he will still have no difficulty in seeing
that he asserts, in the most distinct manner, that which is denied
by the author whom we have before quoted, the propriety and
necessity of assuming the existence of an end as our guide in the
study of animal organization.
4. It appears to me, therefore, that whether we judge from the
arguments, the results, the practice of physiologists, their
speculative opinions, or those of the philosophers of a wider field,
we are led to the same conviction, that in the organized world we
may and must adopt the belief that organization exists for its
purpose, and that the apprehension of the purpose may guide us in
seeing the meaning of the organization. And I now proceed to show
how this principle has been brought into additional clearness and
use by Cuvier.
In doing this, I may, perhaps, be allowed to make a reflection of a
kind somewhat different from the preceding remarks, though suggested
by them. In another work,[122\17] I endeavored to show that those
who have been discoverers in science have generally had minds, the
disposition of which was to believe in an intelligent Maker of the
universe; and that the scientific speculations which produced an
opposite tendency, were generally those which, though they might
deal familiarly with known physical truths, and conjecture boldly
with regard to the unknown, did not add to the number of solid
generalizations. In order to judge whether this remark is distinctly
applicable in the case now considered, I should have to estimate
Cuvier in comparison with other physiologists of his time, which I
do not presume to do. But I may {492} observe, that he is allowed by
all to have established, on an indestructible basis, many of the
most important generalizations which zoology now contains; and the
principal defect which his critics have pointed out, has been, that
he did not generalize still more widely and boldly. It appears,
therefore, that he cannot but be placed among the great discoverers
in the studies which he pursued; and this being the case, those who
look with pleasure on the tendency of the thoughts of the greatest
men to an Intelligence far higher than their own, most be gratified
to find that he was an example of this tendency; and that the
acknowledgement of a creative purpose, as well as a creative power,
not only entered into his belief but made an indispensable and
prominent part of his philosophy.
[Note 122\17: _Bridgewater Treatise_, B. iii. c. vii. and viii. On
Inductive Habits of Thought, and on Deductive Habits of Thought.]
_Sect._ 3.--_Establishment and Application of the Principle of the
Conditions of Existence of Animals.--Cuvier._
WE have now to describe more in detail the doctrine which Cuvier
maintained in opposition to such opinions as we have been speaking
of; and which, in his way of applying it, we look upon as a material
advance in physiological knowledge, and therefore give to it a
distinct place in our history. "Zoology has," he says,[123\17] in
the outset of his _Règne Animal_, "a principle of reasoning which is
peculiar to it, and which it employs with advantage on many
occasions: this is the principle of _the Conditions of Existence_,
vulgarly the principle of _Final Causes_. As nothing can exist if it
do not combine all the conditions which render its existence
possible, the different parts of each being must be co-ordinated in
such a manner as to render the total being possible, not only in
itself, but in its relations to those which surround it; and the
analysis of these conditions often leads to general laws, as clearly
demonstrated as those which result from calculation or from
experience."
[Note 123\17: _Règne An._ p. 6.]
This is the enunciation of his leading principle in general terms.
To our ascribing it to him, some may object on the ground of its
being self-evident in its nature,[124\17] and having been very
anciently applied. But to this we reply, that the principle must be
considered as a real discovery in the hands of him who first shows
how to make it an instrument of other discoveries. It is true, in
other cases as well as in this, that some vague apprehension, of
true general principles, such as _à_ {493} _priori_ considerations
can supply, has long preceded the knowledge of them as real and
verified laws. In such a way it was seen, before Newton, that the
motions of the planets must result from attraction; and so, before
Dufay and Franklin, it was held that electrical actions must result
from a fluid. Cuvier's merit consisted, not in seeing that an animal
cannot exist without combining all the conditions of its existence;
but in perceiving that this truth may be taken as a guide in our
researches concerning animals;--that the mode of their existence may
be collected from one part of their structure, and then applied to
interpret or detect another part. He went on the supposition not
only that animal forms have _some_ plan, _some_ purpose, but that
they have an intelligible plan, a discoverable purpose. He proceeded
in his investigations like the decipherer of a manuscript, who makes
out his alphabet from one part of the context, and then applies it
to read the rest. The proof that his principle was something very
different from an identical proposition, is to be found in the fact,
that it enabled him to understand and arrange the structures of
animals with unprecedented clearness and completeness of order; and
to restore the forms of the extinct animals which are found in the
rocks of the earth, in a manner which has been universally assented
to as irresistibly convincing. These results cannot flow from a
trifling or barren principle; and they show us that if we are
disposed to form such a judgment of Cuvier's doctrine, it must be
because we do not fully apprehend its import.
[Note 124\17: Swainson. _Study of Nat. Hist._ p. 85.]
To illustrate this, we need only quote the statement which he makes,
and the uses to which he applies it. Thus in the Introduction to his
great work on _Fossil Remains_ he says, "Every organized being forms
an entire system of its own, all the parts of which mutually
correspond, and concur to produce a certain definite purpose by
reciprocal reaction, or by combining to the same end. Hence none of
these separate parts can change their forms without a corresponding
change in the other parts of the same animal; and consequently each of
these parts, taken separately, indicates all the other parts to which
it has belonged. Thus, if the viscera of an animal are so organized as
only to be fitted for the digestion of recent flesh, it is also
requisite that the jaws should be so constructed as to fit them for
devouring prey; the claws must be constructed for seizing it and
tearing it to pieces; the teeth for cutting and dividing its flesh;
the entire system of the limbs or organs of motion for pursuing and
overtaking it; and the organs of sense for discovering it at a
distance. Nature must also have endowed the brain of the animal with
instincts sufficient for concealing itself and for laying plans to
{494} catch its necessary victims."[125\17] By such considerations he
has been able to reconstruct the whole of many animals of which parts
only were given;--a positive result, which shows both the reality and
the value of the truth on which he wrought.
[Note 125\17: _Theory of the Earth_, p. 90.]
Another great example, equally showing the immense importance of
this principle in Cuvier's hands, is the reform which, by means of
it, he introduced into the classification of animals. Here again we
may quote the view he himself has given[126\17] of the character of
his own improvements. In studying the physiology of the natural
classes of vertebrate animals, he found, he says, "in the respective
quantity of their respiration, the reason of the quantity of their
motion, and consequently of the kind of locomotion. This, again,
furnishes the reason for the forms of their skeletons and muscles;
and the energy of their senses, and the force of their digestion,
are in a necessary proportion to the same quantity. Thus a division
which had till then been established, like that of vegetables, only
upon observation, was found to rest upon causes appreciable, and
applicable to other cases." Accordingly, he applied this view to
invertebrates;--examined the modifications which take place in their
organs of circulation, respiration, and sensation; and having
calculated the necessary results of these modifications, he deduced
from it a new division of those animals, in which they are arranged
according to their true relations.
[Note 126\17: _Hist. Sc. Nat._ i. 293.]
Such have been some of the results of the principle of the
Conditions of Existence, as applied by its great assertor.
It is clear, indeed, that such a principle could acquire its
practical value only in the hands of a person intimately acquainted
with anatomical details, with the functions of the organs, and with
their variety in different animals. It is only by means of such
nutriment that the embryo truth could be developed into a vast tree
of science. But it is not the less clear, that Cuvier's immense
knowledge and great powers of thought led to their results, only by
being employed under the guidance of this master-principle: and,
therefore, we may justly consider it as the distinctive feature of
his speculations, and follow it with a gratified eye, as the thread
of gold which runs through, connects, and enriches his zoological
researches:--gives them a deeper interest and a higher value than
can belong to any view of the organical sciences, in which the very
essence of organization is kept out of sight. {495}
The real philosopher, who knows that all the kinds of truth are
intimately connected, and that all the best hopes and encouragements
which are granted to our nature must be consistent with truth, will be
satisfied and confirmed, rather than surprised and disturbed, thus to
find the Natural Sciences leading him to the borders of a higher
region. To him it will appear natural and reasonable, that after
journeying so long among the beautiful and orderly laws by which the
universe is governed, we find ourselves at last approaching to a
Source of order and law, and intellectual beauty:--that, after
venturing into the region of life and feeling and will, we are led to
believe the Fountain of life and will not to be itself unintelligent
and dead, but to be a living Mind, a Power which aims as well as acts.
To us this doctrine appears like the natural cadence of the tones to
which we have so long been listening; and without such a final strain
our ears would have been left craving and unsatisfied. We have been
lingering long amid the harmonies of law and symmetry, constancy and
development; and these notes, though their music was sweet and deep,
must too often have sounded to the ear of our moral nature, as vague
and unmeaning melodies, floating in the air around us, but conveying
no definite thought, moulded into no intelligible announcement. But
one passage which we have again and again caught by snatches, though
sometimes interrupted and lost, at last swells in our ears full,
clear, and decided; and the religious "Hymn in honor of the Creator,"
to which Galen so gladly lent his voice, and in which the best
physiologists of succeeding times have ever joined, is filled into a
richer and deeper harmony by the greatest philosophers of these later
days, and will roll on hereafter the "perpetual song" of the temple of
science.
{{497}}
BOOK XVIII.
_THE PALÆTIOLOGICAL SCIENCES._
HISTORY OF GEOLOGY.
Di quibus imperium est animarum, Umbræque silentes,
Et Chaos, et Phlegethon, loca nocte silentia late,
Sit mihi fas audita loqui; sit, numine vestro
Pandere res alta terrâ et caligine mersas.
VIRGIL. _Æn._ vi. 264.
Ye Mighty Ones, who sway the Souls that go
Amid the marvels of the world below!
Ye, silent Shades, who sit and hear around!
Chaos! and Streams that burn beneath the ground!
All, all forgive, if by your converse stirred,
My lips shall utter what my ears have heard;
If I shall speak of things of doubtful birth,
Deep sunk in darkness, as deep sunk in earth.
{{499}}
INTRODUCTION.
_Of the Palætiological Sciences._
WE now approach the last Class of Sciences which enter into the
design of the present work; and of these, Geology is the
representative, whose history we shall therefore briefly follow. By
the Class of Sciences to which I have referred it, I mean to point
out those researches in which the object is, to ascend from the
present state of things to a more ancient condition, from which the
present is derived by intelligible causes.
The sciences which treat of causes have sometimes been termed
_ætiological_, from αἰτία, _a cause_: but this term would not
sufficiently describe the speculations of which we now speak; since
it might include sciences which treat of Permanent Causality, like
Mechanics, as well as inquiries concerning Progressive Causation.
The investigations which I now wish to group together, deal, not
only with the possible, but with the actual past; and a portion of
that science on which we are about to enter, Geology, has properly
been termed _Palæontology_, since it treats of beings which formerly
existed.[1\18] Hence, combining these two notions,[2\18]
_Palætiology_ appears to be a term not inappropriate, to describe
those speculations which thus refer to actual past events, and
attempt to explain them by laws of causation.
[Note 1\18: Πάλαι, ὄντα]
[Note 2\18: Πάλαι, αἰτία]
Such speculations are not confined to the world of inert matter; we
have examples of them in inquiries concerning the monuments of the
art and labor of distant ages; in examinations into the origin and
early progress of states and cities, customs and languages; as well
as in researches concerning the causes and formations of mountains
and rocks, the imbedding of fossils in strata, and their elevation
from the bottom of the ocean. All these speculations are connected
by this bond,--that they endeavor to ascend to a past state of
things, by the aid of the evidence of the present. In asserting,
with Cuvier, that {500} "The geologist is an antiquary of a new
order," we do not mark a fanciful and superficial resemblance of
employment merely, but a real and philosophical connexion of the
principles of investigation. The organic fossils which occur in the
rock, and the medals which we find in the ruins of ancient cities,
are to be studied in a similar spirit and for a similar purpose.
Indeed, it is not always easy to know where the task of the
geologist ends, and that of the antiquary begins. The study of
ancient geography may involve us in the examination of the causes by
which the forms of coasts and plains are changed; the ancient mound
or scarped rock may force upon us the problem, whether its form is
the work of nature or of man; the ruined temple may exhibit the
traces of time in its changed level, and sea-worn columns; and thus
the antiquarian of the earth may be brought into the very middle of
the domain belonging to the antiquarian of art.
Such a union of these different kinds of archæological
investigations has, in fact, repeatedly occurred. The changes which
have taken place in the temple of Jupiter Serapis, near Puzzuoli,
are of the sort which have just been described; and this is only one
example of a large class of objects;--the monuments of art converted
into records of natural events. And on a wider scale, we find
Cuvier, in his inquiries into geological changes, bringing together
historical and physical evidence. Dr. Prichard, in his _Researches
into the Physical History of Man_, has shown that to execute such a
design as his, we must combine the knowledge of the physiological
laws of nature with the traditions of history and the philosophical
comparison of languages. And even if we refuse to admit, as part of
the business of geology, inquiries concerning the origin and
physical history of the present population of the globe; still the
geologist is compelled to take an interest in such inquiries, in
order to understand matters which rigorously belong to his proper
domain; for the ascertained history of the present state of things
offers the best means of throwing light upon the causes of _past_
changes. Mr. Lyell quotes Dr. Prichard's book more frequently than
any geological work of the same extent.
Again, we may notice another common circumstance in the studies
which we are grouping together as palætiological, diverse as they
are in their subjects. In all of them we have the same kind of
manifestations of a number of successive changes, each springing out
of a preceding state; and in all, the phenomena at each step become
more and more complicated, by involving the results of all that has
preceded, modified by supervening agencies. The general aspect of
all these {501} trains of change is similar, and offers the same
features for description. The relics and ruins of the earlier states
are preserved, mutilated and dead, in the products of later times.
The analogical figures by which we are tempted to express this
relation are philosophically true. It is more than a mere fanciful
description, to say that in languages, customs, forms of Society,
political institutions, we see a number of formations super-imposed
upon one another, each of which is, for the most part, an assemblage
of fragments and results of the preceding condition. Though our
comparison might be bold, it would be just, if we were to assert,
that the English language is a conglomerate of Latin words, bound
together in a Saxon cement; the fragments of the Latin being partly
portions introduced directly from the parent quarry, with all their
sharp edges, and partly pebbles of the same material, obscured and
shaped by long rolling in a Norman or some other channel. Thus the
study of palætiology in the materials of the earth, is only a type
of similar studies with respect to all the elements, which, in the
history of the earth's inhabitants, have been constantly undergoing
a series of connected changes.
But, wide as is the view which such considerations give us of the
class of sciences to which geology belongs, they extend still
further. "The science of the changes which have taken place in the
organic kingdoms of nature," (such is the description which has been
given of Geology,[3\18]) may, by following another set of
connexions, be extended beyond "the modifications of the surface of
our own planet." For we cannot doubt that some resemblance of a
closer or looser kind, has obtained between the changes and causes
of change, on other bodies of the universe, and on our own. The
appearances of something of the kind of volcanic action on the
surface of the moon, are not to be mistaken. And the inquiries
concerning the origin of our planet and of our solar system,
inquiries to which Geology irresistibly impels her students, direct
us to ask what information the rest of the universe can supply,
bearing upon this subject. It has been thought by some, that we can
trace systems, more or less like our solar system, in the process of
formation; the nebulous matter, which is at first expansive and
attenuated, condensing gradually into suns and planets. Whether this
_Nebular Hypothesis_ be tenable or not, I shall not here inquire;
but the discussion of such a question would be closely connected
with {502} geology, both in its interests and in its methods. If men
are ever able to frame a science of the past changes by which the
universe has been brought into its present condition, this science
will be properly described as _Cosmical Palætiology_.
[Note 3\18: Lyell, _Principles of Geology_, p. 1.]
These palætiological sciences might properly be called _historical_,
if that term were sufficiently precise: for they are all of the
nature of history, being concerned with the succession of events:
and the part of history which deals with the past causes of events,
is, in fact, a moral palætiology. But the phrase _Natural History_
has so accustomed us to a use of the word _history_ in which we have
nothing to do with time, that, if we were to employ the word
_historical_ to describe the palætiological sciences, it would be in
constant danger of being misunderstood. The fact is, as Mohs has
said, that Natural History, when systematically treated, rigorously
excludes all that is _historical_; for it classes objects by their
permanent and universal properties, and has nothing to do with the
narration of particular and casual facts. And this is an
inconsistency which we shall not attempt to rectify.
All palætiological sciences, since they undertake to refer changes
to their causes, assume a certain classification of the phenomena
which change brings forth, and a knowledge of the operation of the
causes of change. These phenomena, these causes, are very different,
in the branches of knowledge which I have thus classed together. The
natural features of the earth's surface, the works of art, the
institutions of society, the forms of language, taken together, are
undoubtedly a very wide collection of subjects of speculation; and
the kinds of causation which apply to them are no less varied. Of
the causes of change in the inorganic and organic world,--the
peculiar principles of Geology--we shall hereafter have to speak. As
these must be studied by the geologist, so, in like manner, the
tendencies, instincts, faculties, principles, which direct man to
architecture and sculpture, to civil government, to rational and
grammatical speech, and which have determined the circumstances of
his progress in these paths, must be in a great degree known to the
Palætiologist of Art, of Society, and of Language, respectively, in
order that he may speculate soundly upon his peculiar subject. With
these matters we shall not here meddle, confining ourselves, in our
exemplification of the conditions and progress of such sciences, to
the case of Geology.
The journey of survey which we have attempted to perform over the
field of human knowledge, although carefully directed according to
the paths and divisions of the physical sciences, has already {503}
conducted us to the boundaries of physical science, and gives us a
glimpse of the region beyond. In following the history of Life, we
found ourselves led to notice the perceptive and active faculties of
man; it appeared that there was a ready passage from physiology to
psychology, from physics to metaphysics. In the class of sciences
now under notice, we are, at a different point, carried from the
world of matter to the world of thought and feeling,--from things to
men. For, as we have already said, the science of the causes of
change includes the productions of Man as well as of Nature. The
history of the earth, and the history of the earth's inhabitants, as
collected from phenomena, are governed by the same principles. Thus
the portions of knowledge which seek to travel back towards the
origin, whether of inert things or of the works of man, resemble
each other. Both of them treat of events as connected by the thread
of time and causation. In both we endeavor to learn accurately what
the present is, and hence what the past has been. Both are
_historical_ sciences in the same sense.
It must be recollected that I am now speaking of history as
ætiological;--as it investigates causes, and as it does this in a
scientific, that is, in a rigorous and systematic, manner. And I may
observe here, though I cannot now dwell on the subject, that all
ætiological sciences will consist of three portions; the Description
of the facts and phenomena;--the general Theory of the causes of
change appropriate to the case;--and the Application of the theory
to the facts. Thus, taking Geology for our example, we must have,
first _Descriptive_ or _Phenomenal_ Geology; next, the exposition of
the general principles by which such phenomena can be produced,
which we may term _Geological Dynamics_; and, lastly, doctrines
hence derived, as to what have been the causes of the existing state
of things, which we may call _Physical Geology_.
These three branches of geology may be found frequently or
constantly combined in the works of writers on the subject, and it
may not always be easy to discriminate exactly what belongs to each
subject.[4\18] But the analogy of this science with others, its
present {504} condition and future fortunes, will derive great
illustration from such a distribution of its history; and in this
point of view, therefore, we shall briefly treat of it; dividing the
history of Geological Dynamics, for the sake of convenience, into
two Chapters, one referring to inorganic, and one to organic,
phenomena.
[Note 4\18: The Wernerians, in distinguishing their study from
_Geology_, and designating it as _Geognosy_, the _knowledge_ of the
earth, appear to have intended to select Descriptive Geology for
their peculiar field. In like manner, the original aim of the
Geological Society of London, which was formed (1807) "with a view
to record and multiply observations," recognized the possibility of
a Descriptive Geology separate from the other portions of the
science.]
{{505}}
DESCRIPTIVE GEOLOGY.
CHAPTER I.
PRELUDE TO SYSTEMATIC DESCRIPTIVE GEOLOGY.
_Sect._ 1.--_Ancient Notices of Geological Facts._
THE recent history of Geology, as to its most important points, is
bound up with what is doing at present from day to day; and that
portion of the history of the science which belongs to the past, has
been amply treated by other writers.[5\18] I shall, therefore, pass
rapidly over the series of events of which this history consists;
and shall only attempt to mention what may seem to illustrate and
confirm my own view of its state and principles.
[Note 5\18: As MM. Lyell, Fitton, Conybeare, in our own country.]
Agreeably to the order already pointed out, I shall notice, in the
first place, Phenomenal Geology, or the description of the facts, as
distinct from the inquiry into their causes. It is manifest that
such a merely descriptive kind of knowledge may exist; and it
probably will not be contested, that such knowledge ought to be
collected, before we attempt to frame theories concerning the causes
of the phenomena. But it must be observed, that we are here speaking
of the formation of a _science_; and that it is not a collection of
miscellaneous, unconnected, unarranged knowledge that can be
considered as constituting science; but a methodical, coherent, and,
as far as possible, complete body of facts, exhibiting fully the
condition of the earth as regards those circumstances which are the
subject matter of geological speculation. Such a Descriptive Geology
is a pre-requisite to Physical Geology, just as Phenomenal Astronomy
necessarily preceded Physical Astronomy, or as Classificatory Botany
is a necessary accompaniment to Botanical Physiology. We may observe
also that Descriptive Geology, such as we now speak of, is one of
the classificatory sciences, like {506} Mineralogy or Botany: and
will be found to exhibit some of the features of that class of
sciences.
Since, then, our History of Descriptive Geology is to include only
systematic and scientific descriptions of the earth or portions of
it, we pass over, at once, all the casual and insulated statements
of facts, though they may be geological facts, which occur in early
writers; such, for instance, as the remark of Herodotus,[6\18] that
there are shells in the mountains of Egypt; or the general
statements which Ovid puts in the mouth of Pythagoras:[7\18]
Vidi ego quod fuerat solidissima tellus,
Esse fretum; vidi factas ex æquore terras,
Et procul a pelago conchæ jacuere marinæ.
[Note 6\18: ii. 12.]
[Note 7\18: Met. xv. 262.]
We may remark here already how generally there are mingled with
descriptive notices of such geological facts, speculations
concerning their causes. Herodotus refers to the circumstance just
quoted, for the purpose of showing that Egypt was formerly a gulf of
the sea; and the passage of the Roman poet is part of a series of
exemplifications which he gives of the philosophical tenet, that
nothing perishes but everything changes. It will be only by constant
attention that we shall be able to keep our provinces of geology
distinct.
_Sect._ 2.--_Early Descriptions and Collections of Fossils._
IF we look, as we have proposed to do, for systematic and exact
knowledge of geological facts, we find nothing which we can properly
adduce till we come to modern times. But when facts such as those
already mentioned, (that sea-shells and other marine objects are
found imbedded in rocks,) and other circumstances in the structure
of the Earth, had attracted considerable attention, the exact
examination, collection, and record of these circumstances began to
be attempted. Among such steps in Descriptive Geology, we may notice
descriptions and pictures of fossils, descriptions of veins and
mines, collections of organic and inorganic fossils, maps of the
mineral structure of countries, and finally, the discoveries
concerning the superposition of strata, the constancy of their
organic contents, their correspondence in different countries, and
such great general relations of the materials and features of the
earth as have been discovered up to the present time. {507} Without
attempting to assign to every important advance its author, I shall
briefly exemplify each of the modes of contributing to descriptive
geology which I have just enumerated.