The Dawn of Reason Part 3

Certain acc.u.mulations of nerve-cells called ganglions (ganglia) are to be found scattered throughout the structure of animals. Experiment and observation teach that these ganglia subserve a governing influence over nerve-action; hence, they are called nerve-centres.

Nerve-tissue is found in all animals above and including Hydrozoa, according to Romanes;[24] I am inclined to believe, however, that it is present in animals even lower than Hydrozoa, for I have been able, on more than one occasion, to verify Professor Clark's observations in regard to the protozoan, _Stentor polymorphus_, which, as he a.s.serts,[25] has a well-developed nervous system. Moreover, I have seen, in my opinion, unquestionable acts of conscious determination enacted by this little creature, as I will point out further along in this chapter.

[24] Romanes, _Mental Evolution in Animals_, p. 24.

[25] Clark, _Mind in Nature_, p. 64 _et seq._

Nerve-tissue has the peculiar faculty of transmitting impressions made upon it by stimuli. When a nerve is acted on by a stimulus, the impression wave is transmitted along the in-going nerve to the ganglion; here, the stimulus is transferred to the out-going nerve, which, going to the muscle, causes it to contract.

This form of nerve-action is called reflex action, and reflex action is, in the beginning, the germ from which spring volition (choice) and all of the higher psychical attributes.

Again, it is to be observed, as animals become more highly organized, that nerves have the power of discriminating between stimuli, and "it is this power of discriminating between stimuli," as Romanes puts it, "_irrespective of their relative mechanical intensities_, that const.i.tutes the physiological aspect of choice" (volition). It is also through the faculty of discrimination that the special senses, upon which the entire psychical structure depends, have been evolved.

The fact of this power of discrimination has been so clearly and so beautifully demonstrated by Romanes, that I present his experiment and observations, as detailed by him in his magnificent work, _Mental Evolution in Animals_:--

"I have observed that if a sea-anemone is placed in an aquarium tank, and allowed to fasten on one side of the tank near the surface of the water, and if a jet of sea-water is made to play continuously and forcibly upon the anemone from above, the result of course is that the animal becomes surrounded with a turmoil of water and air-bubbles. Yet, after a short time, it becomes so accustomed to this turmoil that it will expand its tentacles in search of food, just as it does when placed in calm water. If now one of the expanded tentacles is gently touched with a solid body, all the others close around that body, in just the same way as they would were they expanded in calm water. That is to say, the tentacles are able to discriminate between the stimulus which is applied by the turmoil of the water and that which is supplied by their contact with the solid body, and they respond to the latter stimulus notwithstanding that it is of incomparably less intensity than the former."[26]

[26] Romanes, _Mental Evolution in Animals_, pp. 48, 49.

When a stimulus pa.s.ses over a nerve to a ganglion, it leaves upon it an impression which remains for a shorter or longer time as the stimulus is great or small. Now, when a stimulus is again applied to the nerve, the impression wave follows in the footsteps, as it were, of the first impression wave, and the ganglion reflects or transfers it just as before, thus showing that nerve has another peculiar quality--that of _memory_.

Again, when two or more reflexes are excited by the same stimulus or stimuli, the ganglion learns to a.s.sociate one with the other, thus showing that it possesses another quality--that of the a.s.sociation of ideas (stimuli and reflexes).

All of these operations are, in their beginnings, exceedingly simple; yet, as organisms increase in complexity, these simple beginnings become more complex and more highly developed.

Heretofore, the operations described have been entirely ganglionic (reflex) and utterly without that which we call consciousness. Now, since consciousness, as I understand it, is simply a knowledge of existence, and since this knowledge of existence is only to be had through sensual perceptions, and, since sensual perceptions are excited undoubtedly by coordinated stimuli, then, "there cannot be coordination of many stimuli without some ganglion through which they are all brought into relation.

In the process of bringing these into relation, this ganglion must be subject to the influence of each--must undergo many changes. And the quick succession of changes in a ganglion, implying as it does perpetual experiences of differences and likenesses, const.i.tute the raw material of consciousness."[27]

[27] Spencer, _Principles of Psychology_, Vol. I. p. 435.

However quick this succession of changes may be, there must be an interval of time between the application of the stimulus and the response to that stimulus, hence, the element of time enters into all psychical operations that are not distinctly reflex. Even in the reflexes there is a time element, but it is distinctly shorter than the time interval that enters into the make-up of a conscious psychical operation. This can easily be demonstrated, as has been done, time and again, by actual experiment.

"With this gradual dawn of consciousness as revealed to subjective a.n.a.lysis, we should expect some facts of physiology, or of objective a.n.a.lysis, to correspond; and this we do find. For in our own organisms we know that reflex actions are not accompanied by consciousness, although the complexity of the nerve-muscular systems concerned in these actions may be very considerable. Clearly, therefore, it is not mere complexity of ganglionic action that determines consciousness. What, then, is the difference between the mode of operation of the cerebral hemispheres and that of the lower ganglia, which may be taken to correspond with the great subjective distinction between the consciousness which may attend the former and the no-consciousness which is invariably characteristic of the latter? I think that the only difference that can be pointed to is a difference of rate of time."[28]

[28] Romanes, _Mental Evolution in Animals_, pp. 72, 73.

The gradual cultivation of the senses (evolution), during which the special adaptations of their motor reactions are gradually developed, is a necessary prerequisite to the formation and elaboration of conscious volition.[29] In the foregoing pages I have very briefly discussed this cultivation of the senses and the development of their motor reactions. I have likewise outlined the origin of volition from sensual perceptions; it now becomes necessary in this discussion of mind, in the lower animals, to study those organisms in which volition (choice) first makes its appearance in the shape of conscious determination.

[29] Maudsley, _Physiology of Mind_, p. 247.

_Stentor polymorphus_ is exceedingly interesting on more than one account. Its queer, trumpet-like shape, with its flaring, bell-like, open mouth (if I may use such a term to indicate its entire cephalic extremity), surmounted by rows of vibratile cilia, its pulsating contractile vesicle, its ability to move from place to place by swimming, are all interesting features; but, when it is ascertained to be the first creature in the entire Animal Kingdom in which a true nervous system is to be found, then it becomes doubly interesting.

This protozoan has been a favorite subject for study with microscopists, but Professor Clark of Harvard was the first observer to note and call attention to its nerve-supply. Says he in his note calling attention to this discovery:--

"The digestive and circulatory systems are the only parts of the organization essential to life that are known to investigators; but recently I have been led to believe that I have discovered the _nervous system_, or at least a part of it, and that too in the very region of the body where there is the most activity, and therefore more likely than elsewhere to have this system most strongly developed. Immediately within the edge of the disk (_bell_) there runs all around a narrow faint band, which lies so close to the surface that it is difficult to determine precisely that it is not actually superficial. From this band there arise, at nearly equal distances all round, about a dozen excessively faint thin stripes, which converge in a general direction toward the mouth."[30]

[30] Clark, _Mind in Nature_, pp. 64, 65.

This band Professor Clark very correctly, as I believe, a.s.sumes to be a part of Stentor's nervous system; for, with a medium high-power lens (500) I have been able to make out ganglionic enlargements both in the circular band and in the stripes. These ganglia are the brain of this infusorian. When the animalcule is stained with eosin, the nervous system can very readily be made out and followed throughout all of its ramifications.

On one occasion, while I was studying the contractile vesicle (heart) of one of these animalcules, I saw it evince what seemed to me to be unquestionable evidences of conscious determination.

Just above the creature, which was resting in its tube (it builds a gelatinous tube into which it shrinks when alarmed or disturbed in any way), there was a bit of alga, from which ripened spores were being given off. Some of these spores were ruptured (probably by my manipulations) and starch grains were escaping therefrom.

The Stentor, from its location below the alga, could not reach the starch grains without altering its position. I saw it elevate itself in its tube until it touched the starch grains with its cilia. With these it swept a grain into its mouth, and then sank down in its tube. I thought, at first, that this was the result of accident, but when the creature again elevated itself, and again captured a starch grain, I was compelled to admit design!

By some sense, it had discovered the presence of starch, which it recognized to be food; it could not get at this food without making a change in its position, which, therefore, it immediately proceeded to do!

Here was an act which required, so it seemed to me, correlative ideation, and which was doubly surprising, because occurring in an animal of such extremely simple organization. This observation was substantiated, however, by the testimony of Professor Carter, an English biologist, which came to my notice a week or so thereafter. This investigator witnessed a similar act in an animalcule belonging, it is true, to another family, but which is almost, if not quite, as simple in its organization as Stentor. He does not designate the particular rhizopods that he had under observation, yet from his language, we are able to cla.s.sify them approximately. His account is so very interesting that I take the liberty of quoting him in full.

"On one occasion, while investigating the nature of some large, transparent, spore-like elliptical cells (fungal?) whose protoplasm was rotating, while it was at the same time charged with triangular grains of starch, I observed some actinophorous rhizopods creeping about them, which had similar shaped grains of starch in their interior; and having determined the nature of these grains by the addition of iodine, I cleansed the gla.s.ses, and placed under the microscope a new portion of the sediment from the basin containing these cells and actinophryans for further examination, when I observed one of the spore-like cells had become ruptured, and that a portion of its protoplasm, charged with the triangular starch grains, was slightly protruding through the crevice.

It then struck me that the actinophryans had obtained their starch grains from this source; and while looking at the ruptured cell, an _actinophrys_ made its appearance, and creeping round the cell, at last arrived at the crevice, from which it extricated one of the grains of starch mentioned, and then crept off to a good distance. Presently, however, it returned to the same cell; and although there were now no more starch grains protruding, the _actinophrys_ managed again to extract one from the interior through the crevice. All this was repeated several times, showing that the _actinophrys_ instinctively knew that those were nutritious grains, that they were contained in this cell, and that, although each time after incepting a grain it went away to some distance, it knew how to find its way back to the cell again which furnished this nutriment.

"On another occasion I saw an _actinophrys_ station itself close to a ripe spore-cell of _pythium_, which was situated on a filament of _Spirogyra cra.s.sa_; and as the young ciliated monadic germs issued forth one after another from the dehiscent spore-cell, the _actinophrys_ remained by it and caught every one of them, even to the last, when it retired to another part of the field, as if instinctively conscious that there was nothing more to be got at the old place.

"But by far the greatest feat of this kind that ever presented itself to me was the catching of a young _acineta_ by an old sluggish _amoeba_, as the former left its parent; this took place as follows:

"In the evening of the 2d of June, 1858, in Bombay, while looking through a microscope at some _Euglenae_, etc., which had been placed aside for examination in a watch-gla.s.s, my eye fell upon a stalked and triangular _acineta_ (_A. mystacina?_), around which an _amoeba_ was creeping and lingering, as they do when they are in quest of food. But knowing the antipathy that the _amoeba_, like almost every other infusorian, has to the tentacles of the _acineta_, I concluded that the _amoeba_ was not encouraging an appet.i.te for its whiskered companion, when I was surprised to find that it crept up the stem of the _acineta_, and wound itself round its body.

"This mark of affection, too much like that frequently evinced at the other end of the scale, even where there is mind for its control, did not long remain without interpretation. There was a young _acineta_, tender and without poisonous tentacles (for they are not developed at birth), just ready to make its exit from its parent, an exit which takes place so quickly, and is followed by such rapid bounding movements of the non-ciliated _acineta_, that who would venture to say, _a priori_, that a dull, heavy, sluggish _amoeba_ could catch such an agile little thing? But the _amoebae_ are as unerring and unrelaxing in their grasp as they are unrelenting in their cruel inceptions of the living and the dead, when they serve them for nutrition; and thus the _amoeba_, placing itself around the ovarian aperture of the _acineta_, received the young one, nurse-like, in its fatal lap, incepted it, descended from the parent, and crept off. Being unable to conceive at the time that this was such an act of atrocity on the part of the _amoeba_ as the sequel disclosed, and thinking that the young _acineta_ might yet escape, or pa.s.s into some other form in the body of its host, I watched the _amoeba_ for some time afterwards, until the tale ended by the young _acineta_ becoming divided into two parts, and thus in their respective digestive s.p.a.ces ultimately becoming broken down and digested."[31]

[31] Carter, _Annals of Natural History_, 3d Series, 1863, pp. 45, 46; quoted also by Romanes, _Animal Intelligence_, pp. 20, 21.

In the discussion of conscious and unconscious mind, I called attention to the marginal bodies of the nectocalyx of the jelly-fish. These bodies in the "covered-eyed" species are protected by hoods of gelatinous tissue; in the naked-eyed species the hoods are absent. The marginal bodies in both species are practically identical as far as general make-up is concerned, being composed of an acc.u.mulation of brightly-colored pigment-cells, embedded in which are several minute clear crystals. Nerve-fibres connect these bodies with the sensorium ("nerve-ring").

Jelly-fish seek the light, and they can be made to follow a bright light from one side of the aquarium to the other by manipulating the light in the proper manner. Even where a slight current is set up in the water, they will swim against it in their efforts to reach the light.

When two or more of the marginal bodies are excised, no effect seems to follow such excision, but as soon as the last of these bodies is cut out, the creature falls to the bottom of the tank without motion.

When a point in the nectocalyx is irritated with a point of a needle or by a vegetable or mineral irritant, the tip of the manubrium will turn toward, and endeavor to touch, the spot irritated. It does not turn at once, as it would were its movements the result of reflex action; it moves deliberately as though actuated by volition.

The above experiments and observation seem to indicate the presence of conscious determination in the medusa; in fact, there seems to be a distinct element of choice in these psychical manifestations.

While engaged in watching a water-louse, I saw it swim to a hydra, tear off one of its buds, and then swim some distance away to a small bit of mud, behind which it hid until it devoured its tender morsel. Again it swam back to the hydra and plucked from it one of its young; again it swam back to the little mud heap, behind which it once more ensconced itself until it was through with its meal. When we remember that this little creature was among entirely new surroundings (for I dipped it from a pond in a tablespoon full of water which I had poured into a saucer), we will appreciate the fact that the water-louse evinced conscious determination and no little memory. It probably discovered the hydra accidentally; it then, as soon as it had secured its prey, swam away, seeking some spot where it could eat its food without molestation.

But when it sought the hydra again and swam back to its sheltering mud heap, it showed that it remembered the route to and from its source of food supply and its temporary hiding-place.

At the base of a large terminal ganglion in the neuro-cephalic system of the common garden snail, lying immediately below and between its two "horns," will be found, I am satisfied, the centre governing its sense of direction. For, when this portion of this ganglion is destroyed, the snail loses its ability of returning to its home when carried only a short distance away; otherwise, it can find its way back to its domicile when taken what must be to it a very great distance away, indeed.

Beneath the stone coping of a brick wall surrounding the front of my lawn, and which, on the side toward my residence, is almost flush with the ground, many garden snails find a cool, moist, and congenial home.

Last summer I took six of these snails, and, after marking them with a paint of zinc oxide and gum arabic, set them free on the lawn. In time, four of these marked snails returned to their home beneath the stone coping; two of them were probably destroyed by enemies. Again, the same number of snails were marked, after the base of the above-mentioned ganglion had been destroyed, and likewise set free. Although they lived and were to be observed now and then on the trees and bushes of the lawn, none of them ever returned to the place from which they were taken beneath the stone coping. I have performed this experiment repeatedly, always with like results.

These experiments show that the snail is capable of conscious effort; furthermore, they indicate that this little animal is the possessor of a special sense which many of the higher animals have lost in the process of evolution. I refer to the sense of direction, or "homing instinct,"

so-called, which will be treated at length in the chapter on Auxiliary Senses.

Darwin has very beautifully demonstrated the senses of touch, taste, and smell in the angle-worm; provisionally he denies it, however, the senses of sight and hearing.[32] I think he is in error as to these last two senses.

[32] Darwin, _Formation of Vegetable Mould_.

Angle-worms are nocturnal in their habits, hence, we should expect, from the very nature of things, to find them able to differentiate between light and darkness. And experiments show, very conclusively, that they are very sensitive to light. My vermicularium is made of gla.s.s, consequently, when one of its inmates happens to be next to the gla.s.s sides, which very frequently occurs, it is easy to experiment on it with pencils of strong light. If a ray of light is directed upon an angle-worm, it at once begins to show discomfort, and, in a very few moments, it will crawl away from the source of annoyance, and hide in some tunnel deep in the earth of the vermicularium. Again, when the worms are out of their tunnels at night, a strong light s.h.i.+ning on them will at once cause them to seek their holes.