Form and Function Part 6

As a matter of fact Goethe's morphological views are neither very clearly expressed nor very consistent. This comes out in his treatment of the relation between structure and function. Sometimes he takes the view that structure determines function. "The parts of the animal," he writes, "their reciprocal forms, their relations, their particular properties determine the life and habits of the creature."[77] We are not to explain, he says, the tusks of the _Babirussa_ by their possible use, but we must ask how it comes to have tusks. In the same way we must not suppose that a bull has horns in order to gore, but we must investigate the process by which it comes to have horns to gore with. This is the rigorous morphological view. On the other hand he admits elsewhere that function may influence form. Apparently he did not work out his ideas on this point to logical clearness, and Radl[78]

is probably correct in saying that the following quotation with its double a.s.sertion represents most nearly Goethe's position:--

"Also bestimmt die Gestalt die Lebensweise des Thieres, Und die Weise zu leben, sie wirkt auf alle Gestalten Machtig zuruck."[79]

His best piece of purely morphological work was his theory of the metamorphosis of plants. Stripped of its vaguer elements, and of the crude attempt to explain differences in the character of plant organs by differences in the degree of "refinement" of the sap supplied to them, the theory is that stem-leaves, sepals, petals, and stamens are all identical members or appendages. These appendages differ from one another only in shape and in degree of expansion, stem-leaves being expanded, sepals contracted, petals expanded, and so on alternately.

It is equally correct to call a stamen a contracted petal, and a petal an expanded stamen, for no one of the organs is the type of the others, but all equally are varieties of a single abstract plant-appendage.

What Goethe considered he had proved for the appendages of plants he extended to all living things. Every living thing is a complex of living independent beings, which "der Idee, der Anlage nach," are the same, but in appearance may be the same or similar, different or unlike.[80] Not only is there a primordial animal and a primordial plant, schematic forms to which all separate species are referable, but the parts of each are themselves units, which "der Idee nach," are identical _inter se_. This fantasy can hardly be taken seriously as a scientific theory; it seems, however, to have been what guided Goethe in his "discovery" of the vertebral nature of the skull. Just as the fore limb can be h.o.m.ologised with the hind limb, so, reasoning by a.n.a.logy, the skull should be capable of being h.o.m.ologised with the vertebrae. To what ludicrous extremes this doctrine of the repet.i.tion of parts within the organism was pushed we shall see when we consider the theories of the German transcendentalists of the early nineteenth century.

Though Goethe's morphological views were lacking in definiteness he hit upon one or two ideas which proved useful. Thus he enunciated the "law of balance" long before Etienne Geoffroy St Hilaire, the law "that to no part can anything be added, without something being taken away from another part, and _vice versa_."[81] He saw, too, what a help to the interpretation of adult structure the study of the embryo would be, for many bones which are fused in the adult are separate in the embryo.[82] This also was a point to which the later transcendentalists gave considerable attention.

So far we have spoken of Goethe as if he were merely the prophet of formal morphology; we have pointed out how he brought to clear expression the morphological principle implicit in the idea of unity of type, and how he seized upon some important guiding ideas, such as the principle of connections. But Goethe was not a formalist, and he was very far from the static conception of life which is at the base of pure morphology. His interest was not in _Gestalt_ or fixed form, _Bildung_ or form change. He saw that _Gestalt_ was but a momentary phase of _Bildung_, and could be considered apart and in itself only by an abstraction fatal to all understanding of the living thing.

Mephistopheles scoffs at the scholars who would explain a living creature by anatomising it:

"Dann hat er die Theile in seiner Hand, Fehlt leider! nur das geistige Band."[83]

Goethe kept clear of this mistake; he knew that the artist comes nearer to the truth than the a.n.a.lyst.

In the fragment ent.i.tled _Bildung und Umbildung organischer Naturen_ (1807), introductory to a reprint of his paper on the "Metamorphosis of Plants," we get an exposition of his general views on living things. He points out there how we try to understand things by separating them into their parts. We can, it is true, resolve the organism into its structural elements, but we cannot recompose it or endow it with life by joining up the parts. Hence we require some other means of understanding it. "In all ages even among scientific men there can be discerned a yearning to apprehend the living form as such, to grasp the connection of their external visible parts, to interpret them as indications of the inner activity, and so, in a certain measure, to master the whole conceptually." This science which should discover the inner meaning of organic _Bildung_ is called Morphology.[84] In Morphology we should not speak of _Gestalt_ or fixed form, or if we do we should understand by it only a momentary phase of _Bildung_. Form is of interest not in itself but only as the manifestation of the inner activity of the living being. Over development, he says elsewhere, there presides a formative force, a _bildende Kraft_ or _Bildungstrieb_, which works out the idea of the organism. Living things, in his view of them, strive to manifest an idea. They are Nature's works of art--and so, incidentally, they require an artist to interpret them.

This profound conception of the nature of life is applied not only to the growing changing individual but also to the whole changing world of organisms. They are all manifestations of a living shaping power which moulds them. This shaping power, immanent in all life, is conceived to work according to a general plan, and so we get an explanation of the fact that living things seem simply varieties of one common type.

"If we once recognise," says Goethe, "that the creative spirit brings into being and shapes the evolution of the more perfect organic creatures according to a general scheme, is it altogether impossible to represent this original plan if not to the senses at least to the mind...?"[85]

Such an interpretation of the unity of plan reaches perhaps beyond the bounds of science.

[70] _See_ Kohlbrugge, "Hist. krit. Studien uber Goethe als Naturforscher," _Zool. Annalen._ v., 1913, pp.

83-231.

[71] Or re-discovered, according to Kohlbrugge.

[72] Cotta ed., vol. ix., p. 448.

[73] "First Draft of a General Introduction to Comparative Anatomy."

[74] Cotta ed., ix., p. 463.

[75] Cotta ed., p. 478.

[76] _Loc. cit._, p. 491.

[77] _Entwurf_, Cotta ed., ix., p. 465.

[78] _Geschichte der biologischen Theorien_, i., p. 266.

[79] "So the form determines the manner of life of the animal, and the manner of life in its turn reacts powerfully upon all forms."

[80] _Bildung und Umbildung organischer Naturen_, 1807.

[81] Cotta ed., ix., p. 466.

[82] _Loc. cit._, pp. 474-5.

[83] Then he has all the parts within his hand, excepting only, sad to say, the living bond.

[84] Goethe was the inventor of the word.

[85] Cotta ed., ix., p. 490.

CHAPTER V

ETIENNE GEOFFROY SAINT-HILAIRE

E. Geoffrey made an experiment, unsuccessful but instructive. He tried to found a science of pure morphology; he failed: his failure showed, once and for all, that a pure morphology of organic forms is impracticable.

Already, in 1796, in one of his earliest memoirs,[86] Geoffroy was guided by the idea that Nature has formed all living things upon one plan. Organs which seem anomalous are merely modifications of the normal; the trunk of an elephant is formed by the excessively prolonged nostrils, the horn of a rhinoceros is simply a ma.s.s of adhering hairs. In general, however varied their form, all organs are simply variations of a common scheme; Nature employs no new organs.

Organs which are rudimentary, such as the clavicles in the ostrich and the nict.i.tating membrane in man, bear witness to the unity of plan. In this Geoffroy goes no further than his predecessors. They too had recognised h.o.m.ologies of organs; they too had interpreted rudimentary organs as vestiges of an original plan.

In a series of papers published in 1807, Geoffroy took a further step, and sought to establish h.o.m.ologies which were not obvious--h.o.m.ologies, too, not so much of organs as of parts.

These memoirs (published in the _Annales du Museum d'Histoire naturelle_, vols. ix. and x., 1807) dealt with the h.o.m.ology between the bones of the pectoral fin and girdle in fish and the bones of the arm and shoulder-girdle in higher Vertebrates, with the h.o.m.ologies of the bones of the sternum, and with the determination of the pieces of the skull, particularly in the crocodile. All Geoffroy's morphological doctrine is found in them, but for the full expression of his views we must take his chief work, the _Philosophie anatomique_, particularly the first volume (1818). This volume contains, beside the important "Discours preliminaire" and "Introduction" which we shall presently consider in detail, five memoirs, which deal with the various bones connected with the respiratory organs in fishes (the bones of the operculum, of the hyoid, of the branchial arches, of the pectoral girdle), and seek to discover their h.o.m.ologies with corresponding bones in air-breathing Vertebrates.

"Can the organisation of vertebrated animals be referred to one uniform type?" This is the question with which the _Philosophie anatomique_ opens, the question to which the whole book is an answer.

But is it not generally acknowledged by naturalists that Vertebrates are built upon one uniform plan, that, for instance, the fore limb may be modified for running, climbing, swimming, or flying, yet the arrangement of the bones remain the same? How else could there be a "natural method" of cla.s.sification?[87]

But the h.o.m.ologies so drawn repose upon a vague and confused feeling for likenesses; they are not based upon an explicit principle. What general principle can be applied? "Now it is evident that the sole general principle one can apply is given by the position, the relations, and the dependencies of the parts, that is to say, by what I name and include under the term of _connections_." For instance, the part known as the hand in man and generally as the fore foot in other Vertebrates, is the fourth part in order in the anterior member, and its h.o.m.ologue can always be recognised by this fact of its connections (p. xxvi.). The principle of connections serves as a guide in tracing an organ through all its functional transformations, for "an organ can be deteriorated, atrophied, annihilated, but not transposed" (p. x.x.x.).

It is this principle which enables one to follow out in detail the further fundamental conception that in every Vertebrate there are found the same "organic materials," or units of construction. This conception, which Geoffroy calls the _Theorie des a.n.a.logues_ (p. x.x.xii.), is clearly one part of the old idea of the unity of type; it teaches the _unity of composition_ of organic beings, while the _Principe des connexions_ adds the _unity of plan_.

Both conceptions are logically implicit in the vague notion of unity of type; Geoffroy disengaged them, and pushed each to its logical extreme.

Most of the ordinary h.o.m.ologies of structure in air-breathing Vertebrates have already been seized, he continues, for they are more or less obvious, and many intermediate states exist (p. x.x.xiv.). But ordinary methods of comparison fail when the attempt is made to h.o.m.ologise the structure of fishes with that of air-breathing Vertebrates, for the h.o.m.ologies are anything but obvious and no intermediate organs are found.

Most air-breathing Vertebrates have a larynx, a trachea, and bronchi, which are absent in fish; and fish have many parts which seem to be absent in higher Vertebrates. But apply the "Theory of a.n.a.logues"; it teaches that there can be no organ peculiar to fish and not found in other Vertebrates; apply the "Principle of Connections," it will show which organs are h.o.m.ologous in the two types (p. x.x.xv.).

Comparative anatomists, with few exceptions, had hitherto taken man as the type, and referred all structure to his; Geoffroy's principles led him to give preference to no one animal in particular, but to seize upon each part in the species in which it reaches the maximum of its development (p. x.x.xvi.). He is thus led to refer all structures to a generalised abstract type. In this abstract type each organ exists at the maximum of its development, each organ shows all its potentialities realised. In a way, therefore, this type, this abstraction, gives the scheme of the possible transformations of each organ.

It is true Geoffroy does not refer to this "Archetype" in so many words, but it must always have been vaguely present in his mind. He has this idea in his head when he says in one of his later works, "There is, philosophically speaking, only a single animal."[88] The "single animal"

is simply the generalised type.

Having laid down his two principles Geoffroy goes on to apply them to the difficult case of the comparison of the skeleton of fish with the skeleton of the higher Vertebrates. "My present task is to demonstrate that there is no part of the bony framework of fishes that cannot find its a.n.a.logue in the other vertebrated animals."[89] It seems at first sight that many bones are peculiar to fish, formed expressly for performing the functions which fish do not share with higher animals.

These are the bones connected with respiration--the operculum, the branchiostegal rays, the branchial arches, and others. That the peculiar bones should be connected with the respiratory functions is only natural, for the contrast between fish and higher Vertebrates is essentially a contrast between water-breathing and air-breathing animals. Considering first the general form of the skeleton in fish, we are met at once with a difficulty; there is no obvious h.o.m.ologue in fishes of the neck, the trunk, and the abdomen of higher animals. What apparently corresponds to the trunk is in fishes crowded close up under the head. But, after all, it is not of the essence of the vertebrate type to have the trunk and the abdomen attached at definite and invariable distances along the vertebral column--that is a notion surviving from the anatomy which made man its type. The "trunk" differs in position according to the cla.s.s, in quadrupeds, birds, and fishes (p.

9). Now, says Geoffroy, allow me this one hypothesis, that the trunk with its organs can, as it were, move bodily along the vertebral column, so as to be found in one cla.s.s near the front end of the vertebral column, in another about the middle, and in a third near the end, then I can show you in detail that the const.i.tuent parts of this trunk are found in all cla.s.ses to be invariably in the same positions relatively to one another (p. 10). It is important to note this hypothesis of a "metastasis" which Geoffroy makes, for it is the key to the understanding of many of the far-fetched h.o.m.ologies which he tries to establish. It is, of course, clear that this hypothesis is in formal contradiction with his princ.i.p.al hypothesis of the invariability of connections, and that he, so to speak, gets a hold on his fish to apply his principle of connections only by admitting at the very outset an exception to his primary principle. A further application of the hypothesis of metastasis will be noticed below in connection with the determination of the sternum of fishes. We note here an interpretation of the first metastasis in terms of functional adaptation. "The constant and violent action of the tail, if it does not go so far as actually to displace and move forward the internal organs, at least fits in well with an arrangement in which the organs are so disposed" (p. 99).