The Psychic Life of Micro-organisms: A Study in Experimental Psychology

M. Romanes, in his work upon Mental Evolution, without coming to a conclusion so definite as M. Richet, seems to us to have reduced the psychic activity of proto-organisms to within very narrow limits. We are impressed with the fact upon glancing over his Diagram of Mental Evolution : he recognizes nothing but excitability, for example, in the ovule and spermatozoid of man. This is manifestly erroneous. The sexual elements, and especially the spermatozoid, of all unicellular organisms are certainly the ones which show the most highly developed psychical functions: the act of seeking and approaching the ovule, which is frequently situated at quite some distance from where the male element is deposited; the length of road to be traveled; the obstacles to be overcome; all point to faculties in the spermatozoid that are not explainable by simple irritability.

Hitherto, apparently, writers who have essayed to present the psychology of micro-organisms, have contented themselves with schematic notions instead of basing their theories upon the direct observation of these interesting creatures. By the aid of exact data, we have shown that in both vegetable and animal micro-organisms phenomena are encountered which pertain to a highly complex psychology, and which appear quite out of proportion to the minute mass that serves them as a substratum.

We shall first of all advert to the term irritability, which, though long in use, has not in our opinion been happily chosen; since it is in the highest degree ambiguous, and not suggestive of an exact signification. We might call to mind in this connection, the reflection made by Kant upon obscure properties, which he compares to easy-chairs upon which the mind unbends itself and rests. In place of discussing words, let us endeavor to discuss facts.

What are we to understand by irritabilitv ? We ma}' give the expression a very broad or a very restricted meaning. We may make it express the property which every organism possesses, of reacting upon excitation. In this general sense we may say that irritability includes within itself all of psychology, the most highly developed, as well as the most elementary; for upon ultimate analysis every psychical manifestation consists in a response to an excitation. Evidently, it is not in this general and somewhat common sense that M. Richet has intended to employ the word. For a more exact definition, let u's consult his work, of which, a whole chapter, the first, is devoted to this subject; the author enumerates and develops at length the laws of irritability:

1. Every action that modifies the actual condition of a cell is an irritant of that cell. 2. Every external force, provided it has a certain intensity, is capable of inducing cellular irritability. 3. The movement in response to irritation is proportional to the excitation. 4. The movement in response to irritation is, for equal irritations, stronger in proportion as the equilibrium of the cell is less stable; in other words, stronger in proportion as the cell is more excitable.

5. The response to the irritation, .is a movement in the'form of a wave, which has a very short latent period, a period of ascent, correspondingly brief, and a very long period of descent. 6. The movement of the cell upon irritation is, for equal irritations, stronger in proportion as the irritation has been more sudden. 7. The movement in response to a brief irritation lasts much longer than the irritation has lasted. 8. Forces which, alone, appear impotent, become effective when repeated; for they have, in spite of their apparent inefftcacy, increased the excitability of the organism.

The statement of these various laws, gives the term irritability a precision which it lacked. M. Richet had in view particularly the muscular fibres, and the laws of irritability are only supposed to cover a series of physiological experiments made upon the reaction of a striated muscle. They are not, then, hypothetical laws, but are much rather particular experiments generalized and extended to undifferentiated protoplasm. It is proper to remark here, that we have not as yet been able, by means of direct experiments, to ascertain from life the laws of irritability in undifferentiated protoplasm. The experiments made upon this point, — for instance, the experiment causing the protoplasm of a detached cell to contract by means of an electric current, — have not yet been brought to a precise result; for the structure of protoplasm is so delicate and so complex, that even the slightest excitation suffices to produce an alteration, and since it is difficult to distinguish the contraction of the protoplasm from its coagulation. But we shall pass by this subordinate question.

The question now remains, whether the complicated experiments made in muscular physiology, which M. Richet generalizes .and extends to the physiology of all cellules, include and comprehend the whole psychology of an independent organism, and whether we may say with M. Richet, that irritabilit}' (thus understood) represents all of cellular psychology. Plainly not. The numerous facts which we have cited in the foregoing essay, transcend the too narrow limits within which it has been attempted to confine the psychology of the cell. We shall restrict ourselves to the mention of one of these phenomena, to show the complexity of the psychic life of micro-organisms: it is the existence of a power of selection, exercised either in the search for food, or in the manoeu-

vres attending conjugation. This act of selection is a capital phenomenon; we may take it as the characteristic feature of functions pertaining to the nervous system. As Romanes has indeed observed, the power of choice may be regarded as the criterion of psychical faculties. Going farther, we might be able to say that selection comprehends the properties of the nervous cellule, as irritability comprehends the properties of the muscular cellule.

Scientists have endeavored to explain the mechanism of this choice. They have pretended to solve it by saying that it was dependent upon the relation between the chemical composition of the cellule making the choice and the chemical composition of the body selected. Such explanations are purely verbal. Undoubtedly, the faculty of selection, of which protoplasm seems to be possessed, is founded in the character of its chemical composition. Chemistry lies at the basis of physiology, but chemistry does not explain physiology, and it is quite evident that that property which protoplasm possesses of making a choice between several excitations, is a physiological property.

However that may be, we may resume all the foregoing into the statement that every micro-organism has a psychic life, the complexity of which transcends the limits of cellular irritability, from the fact that .every micro-organism possesses a faculty of selection; it chooses its food, as it likewise chooses the animal with which it copulates. M. Richet has defended his opinion in opposition to the one I have propounded, in a note published in the Revue Philosophique for Febuary 1888, wherein he speaks as follows:

At the beginning of his essay upon the Psychic Life of Micro- Organisms (Revtie Philosophique], M. Binet expresses himself as follows: " In the lower beings that represent the simplest forms of life, we find manifestations of an intelligence which greatly transcends the phenomena of cellular irritability. Thus even on the very lowest rounds of the ladder of life, psychic manifestations are very much more complex than is usually believed, and the conception of cellular psychology which some very recent authors have formed, seems to me a very crude analysis of the most delicate of phenomena."

As I have upheld in my Essai de Psychologic Generate, and in some measure — however little — developed this admitedly old idea, that cellular irritability is the beginning of psychical activity, I request the permission to speak in defence of an opinion so roughly handled by M. Binet. Now, it appears to me that M. Binet has allowed himself to become involved in illusion respecting the word cellule. A cell, in the eyes of the embryologist and the morphologist, has a well-defined meaning. But M. Binet does not seem to have comprehended the fact, that for the physiologist and the psychologist, the essential condition of cellular unity is homogeneity. It is possible that the infusoria, the strange story of whose life M. Binet relates to us, are single-celled organisms. I am in no wise qualified to decide as to this; but whether a single cell, or a group of cells, it matters little, in my opinion, provided the single cell is differentiated to the same degree that it would be if composed of several cells not homogeneous.

I appeal to M. Binet himself and to the cuts of his essay. When he shows us an Euglena with eyes, esophagus, mouth, contractile vesicle, contractile reservoir (fig. 6); when he carefully describes the shape of the flagellum, the nettle-like tentacles, the tongueshaped organs, the ocular spots, the trichocysts, and the peristome; when he assumes special nervous centres endowed with various at-' tributes (p. 22): he cannot induce us to admit that the psychology of these complicated organisms is the same as the psychology of the simple cell. I repeat, it is quite immaterial to me that people affirm by the authority of embryology that this or that is a single cell. If that cellule have ocular organs, a nervous system, a mouth, an aesophagus, and a heart, I shall, despite any and every hypothesis of the embryologists, refuse to regard it as being physiologically a homogeneous cell, as is, for example, a muscular fibre.

The size will not affect the matter at all. The same desires, says Montaigne, stir mite and elephant alike. The psychic life of the bee is as complex as that of the whale, and if a microscopic infusory possess eyes, mouth, prickles, and heart, it evidently possesses them in order that it may make ussof them, and accordingly I shall treat it as a complex organism upon the same ground that I do a snail or a grasshopper. Embryology will not force me to the extremity of regarding such a creature as a simple organism because it is derived from a single cell.

In my opinion, therefore, it is that unfortunate word unicellular, that has made M. Binet believe that, Infusoria being unicellular organisms, the elementary psychology of the cellule applied to them. M. Binet has allowed himself to be deceived by a word — a thing that often happens in matters of science. For my own part, in order to avoid any confusion, I would like to say that the elementary psychology of the cellule ought not by rights to be applied to anything except to homogeneous cellules; for the psychology that has to do with complex cells — real organisms with organs and apparatus of their own — must certainly be as complex as the psychology of animals wholly differentiated.

The laws of irritability act in all their simplicity and rigor among simple beings. In fact, in every instance of investigation into the nature of simple organisms, or such as appear simple by the optical instruments at our disposal (a fact that does not always rigorously prove their simplicity), as bacteria, for example, — we find that chemical irritability is the apparently sole law of movement. What else, indeed, are the movements of those bacteria so thoroughly studied by M. Engelmann, if not an affinity for oxygen, in other words the simplest and most universal chemical phenomenon in all nature?

And so the critique of M. Binet will not stand. On the contrary, it seems to be well established that complex organisms, whether single-celled or many-celled, have a psychology corresponding in complexity to the degree of differentiation their organs have attained, while simple beings— and they are simple only if homogeneous — have a simple psychology which is probably contained in the laws of Irritability only. CH. RICHET. My reply to the letter of M. Richer, published in the same number of the Revue Philosophique, may be offered as a general conclusion to my work. With the

omission of all polemical features, it is in substance as follows: In giving the psychology of these microscopic creatures the name of cellular psychology, I have not invented a new term, nor given a new sense to an old one. Quite some time before me, M. Haeckel had made a study of cellular psychology and his investigations, like my own, were based entirely upon the observation of animal and vegetable micro-organisms. Furthermore, micro-organisms being represented by a single cellule (and this doctrine is .now universally accepted), the study of their psychical manifestations can, in my opinion, with perfect propriety be styled cellular psychology.

M. Richet takes exception to the use of the latter expression; but he does so while substituting for the old definition of the word cell, one quite his own. To him, a micro-organism like the Eu- glena, which has an eye, a mouth, an aesophagus, and a contractile vesicle, would not be a cellule. To admit the latter view, means, in his own words, to become involved in illusion respecting the word cellule. In our judgment, the question here is by no means one of optical illusion, but one of verbal definition. What, accordingly, is a cellule? " For the physiologist and psychologist," says M. Richet, " the cellule has not a distinct entity, or, at least, that entity, that unity, lacks an essential condition, namely, homogeneity."

To M. Richet, the cellule is a homogeneous body; a body that comprises differentiated parts is not a cellule. It is unnecessary to remark upon how far the latter conception of a cellule diverges from the usual and commonly accepted definition of the word. Hitherto, scientists have understood by the term cellule, a body made up of the union of two essential parts, a quantity of protoplasm and a nucleus. The scientific world argues as to whether elementary forms exist which do not contain a nucleus and which should be termed cytodes, as proposed by M. Haeckel. The careful observation of micro-organisms by means of perfected technical processes has enabled us to discover hundreds of nuclei in the very cellules which M. Haecke-1 classed among the cytodes. Such is notably the case with many algae and lower-class fungi. The Moners — a group of micro-organisms believed to have no nucleus — grow numerically less and less, in proportion as they are more carefully studied. It is true, we are now no more able

than formerly, to show the presence of a nucleus in bacteria; but that does not prove that the bacteria have none. Our knowledge of the morphology of microscopic organisms is wholly relative, and depends upon the degree of perfection attained by technical science. When we bear in mind that the presence of a nucleus remained for a long time unobserved in organisms several hundred times larger than the bacteria, we ought not to be surprised at having been unable to discover one in these smaller creatures.

We may even go further, and question the material existence of a body formed solely of protoplasm, basing our opinion upon the experiments of Gruber, Nussbaum, and Balbiani, as reported in my article, and upon the more recent observations of Klebs which are in perfect agreement with the results of the investigators just cited. All have shown that the nucleus is an element essential to the life of the cellule, and that, when a fragment of a cellular body stripped of a nucleus is procured by artificial section, this fragment does not reproduce the organs it lost by being severed; it does not heal its wound, it does not refashion its form, and, what is more, at the end of a certain time its protoplasm, being withdrawn from the influence of the nucleus, suffers complete disorganization. These experiments were made not only upon animal micro-organisms, but upon vegetable cells also. They prove the primordial importance of the nucleus in the cellule and thereby render doubtful the existence of cellules deprived of a nucleus.

Since every cellule contains, in all likelihood, two distinct differentiated elements, the protoplasm and the nucleus, which have neither the same physical structure, nor the same chemical nature, nor the same physiological functions, we may understand that it would be exceedingly difficult to name a single instance of a simple homogeneous cellule. It is the proper place to add that neither protoplasm nor nucleus, each regarded by itself, are homogeneous substances. It is unnecessary to enumerate all the investigations that have been made upon this point. Let us call to mind merely the fact that from the morphological point of view protoplasm appears to be composed of two substances, a homogeneous semi-liquid substance and a firmer substance exhibiting, as authorities uppn the subject say, sometimes the form of detached filaments and at others a structure of a reticulate character.

At the present day, accordingly, it is impossible to allow that homogeneous cellules exist, without falling back to Dujardin's theory of the sarcode. There are really no simple organisms, and such as appear so are merely imperfectly known. However, it will not do perhaps to take literally the terms employed by M. Richet. When he speaks of homogeneous cellules it is possible that he wishes to speak merely of cellules in which, aside from the nucleus, no other differentiated organ is to be found.

Now, it is quite important to note that, even of organisms made up simply of protoplasm and nucleus, the psychology is extremely complicated, and is not contained exclusively^ in the laws of irritability. x The Vampyrella Spirogyrce^ classed by Zopf among the animalfungi, and the place of which is still so little known, is a being the body of which iscomposed of protoplasm and nucleus simply. So far no other differentiated organ has been found in this creature, except from one to four contractile vesicles. Employing the terminology of M. Richet, perhaps we ought to call this being a simple cellule; yet this simple cellule has quite a complicated psychology: it exercises choice in the selection of its food, attacking Spirogyra only.

The same is the case with the Monas amyli, which, having neither eye nor mouth, represents to M. Richet a simple cellule; still, the Monas amyli exercises choice in selecting its food, as it feeds exclusively on grains of starch. The structural elements of the tissues do not differ from the micro-organisms whose psychological history I have endeavored to unfold, so much as might be imagined: they show the same powers of selection, and on this point I shall only instance the epithelial cellules of the intestines or the phagocyte cellules, the attributes of which I have described in my essay, and which are able to discriminate, for instance, between bits of fat and particles of coal, absorbing the former and leaving the latter.

I repeat it, therefore, no living cellule, strictly so denned, is a simple cellule, and I do not think that M. Richet has advanced a fitting illustration in mentioning the muscular cell, for the latter is one of the most highly differentiated that there are. I cannot imagine, accordingly, to what elements, to what beings clearly defined, we could apply the simple-cellular psychology reduced to mere irritability, that M. Richet asks me to distinguish from the complex-cellular psychology, which would be exclusively reserved for the animal and vegetable micro-organisms that I have described.

It appears to me that this simple-cellular psychology lacks a foundation; it is a conception of the mind, rather than a study based upon observed facts. In M. Richet's book I find no indication as to what sort of beings he means to distinguish thereby. He contents himself (pp. 20 and 27) with speaking of simple beings without otherwise defining them. Towards the close of his remarks upon my work, M. Richet cites an instance of simple beings, viz., the bacteria; in his judgment, chemical irritability appears to be the sole law conditioning their movements. What are the movements of the bacteria, he asks, if not an affinity for oxygen; in other words, the simplest and most universal chemical phenomenon that exists in all nature?

In our judgment the latter phrase is to be taken metaphorically. We believe that as yet no one has demonstrated that the movements of a living being, in moving towards a distant object, however simple they may be, can be explained merely by a chemical affinity acting between that being and that object. It is certainly not chemical affinity that is acting, but much rather a physiological need. Psychic life, like its substratum, living matter, is, when closely studied, an exceedingly complex subject. This fact is, with me, a profound conviction ; it rests, not upon abstract ideas and methods, but upon the observations that I have given, observations that are not founded upon my own personal authority alone, but which are drawn from the highest authorities, and most of which I have been able to verify with my own eyes.