This would be the extreme case of the action of all the sympathetic and antipathetic relations between human beings (leaving out of account social relations in their narrowest sense, which are merely the safeguards of communities) which are not included in the law of sexual affinity. As K generally increases with the strength of congenital relationship, A has a greater value when the individuals are of the same nationality than when they belong to different nationalities. The value of f t is great in this case, and one can investigate its fluctuations, as, for instance, when two domestic animals of different species are in association; at first it usually stands for violent enmity, or fear of each other (and A has a negative value), whilst later on a friendship may come about.
When K = 0 in the formula
A = K . f t α — β,
then A = 0, which means that between two living beings of origin too remote there may be no trace of sexual attraction.
The provisions of the criminal statute-books, however, in reference to sodomy and bestiality show plainly that even in the case of very remote species K has a value greater than nothing. The formula may apply to two individuals not only not of the same species, but even not of the same order.
It is a new theory that the union of male and female organisms is no mere matter of chance, but is guided by a definite law; and the actual complexities which I have merely suggested show the need for complete investigation into the mysterious nature of sexual attraction.
The experiments of Wilhelm Pfeffer have shown that the male cells of many cryptogams are naturally attracted not merely by the female cells, but also by substances which they have come in contact with under natural conditions, or which have been introduced to them experimentally, in the latter case the substances being sometimes of a kind with which they could not possibly have come in contact, except under the conditions of experiment. Thus the male cells of ferns are attracted not only by the malic acid secreted naturally by the archegonia, but by synthetically prepared malic acid, whilst the male cells of mosses are attracted either by the natural acid of the female cells or by acid prepared from cane sugar. A male cell, which, we know not how, is influenced by the degree of concentration of a solution, moves towards the most concentrated part of the fluid. Pfeffer named such movements “chemotactic” and coined the word “chemotropism” to include these and many other asexual cases of motion stimulated by chemical bodies. There is much to support the view that the attraction exercised by females on males which perceive them at a distance by sense organs is to be regarded as analogous in certain respects with chemotropism.
It seems highly probable that chemotropism is also the explanation of the restless and persistent energy with which for days together the mammalian spermatozoa seek the entrance to the uterus, although the natural current produced from the mucous membrane of the uterus is from within outwards. The spermatozoon, in spite of all mechanical and other hindrances, makes for the egg-cell with an almost incredible certainty. In this connection we may call to mind the prodigious journeys made by many fish; salmon travel for months together, practically without taking any food, from the open sea to the sources of the Rhine, against the current of the river, in order to spawn in localities that are safe and well provided with food.
I have recently been looking at the beautiful sketches which P. Falkenberg has made of the processes of fertilisation in some of the Mediterranean seaweeds. When we speak of the lines of force between the opposite poles of magnets we are dealing with a force no more natural than that which irresistibly attracts the spermatozoon and the egg-cell. The chief difference seems to be that in the case of the attraction between the inorganic substances, strains are set up in the media between the two poles, whilst in the living matter the forces seem confined to the organisms themselves. According to Falkenberg’s observations, the spermatozoa, in moving towards the egg-cells, are able to overcome the force which otherwise would be exercised upon them by a source of light. The sexual attraction, the chemotactic force, is stronger than the phototactic force.
When a union has taken place between two individuals who, according to my formula, are not adapted to each other, if later, the natural complement of either appears the inclination to desert the makeshift at once asserts itself in accordance with an inevitable law of nature. A divorce takes place, as much constitutional, depending on the nature of things, as when, if iron sulphate and caustic potash are brought together, the SO4 ions leave the iron to unite with the potassium. When in nature an adjustment of such differences of potential is about to take place, he who would approve or disapprove of the process from the moral point of view would appear to most to play a ridiculous part.
This is the fundamental idea in Goethe’s “Wahlverwandtschaften” (Elective Affinities), and in the fourth chapter of the first part of that work he makes it the subject of a playful introduction which was full of undreamed of future significance, and the full force of which he was fated himself to experience in later life. I must confess to being proud that this book is the first work to take up his ideas. None the less, it is as little my intention as it was the intention of Goethe to advocate divorce; I hope only to explain it. There are human motives which indispose man to divorce and enable him to withstand it. This I shall discuss later on. The physical side of sex in man is less completely ruled by natural law than is the case with lower animals. We get an indication of this in the fact that man is sexual throughout the year, and that in him there is less trace than even in domestic animals of the existence of a special spring breeding-season.
The law of sexual affinity is analogous in another respect to a well-known law of theoretical chemistry, although, indeed, there are marked differences. The violence of a chemical reaction is proportionate to the mass of the substances involved, as, for instance, a stronger acid solution unites with a stronger basic solution with greater avidity, just as in the case of the union of a pair of living beings with strong maleness and femaleness. But there is an essential difference between the living process and the reaction of the lifeless chemical substances. The living organism is not homogeneous and isotropic in its composition; it is not divisible into a number of small parts of identical properties. The difference depends on the principle of individuality, on the fact that every living thing is an individual, and that its individuality is essentially structural. And so in the vital process it is not as in inorganic chemistry; there is no possibility of a larger proportion forming one compound, a smaller proportion forming another. The organic chemotropism, moreover, may be negative. In certain cases the value of A may result in a negative quantity, that is to say, the sexual attraction may appear in the form of sexual repulsion. It is true that in purely chemical processes the same reaction may take place at different rates. Taking, however, the total failure of some reaction by catalytic interference as the equivalent of a sexual repulsion, it never happens, according to the latest investigations at least, that the interference merely induces the reaction after a longer or shorter interval. On the other hand, it happens frequently that a compound which is formed at one temperature breaks up at another temperature. Here the “direction” of the reaction is a function of the temperature, as, in the vital process, it may be a function of time.
In the value of the factor “t,” the time of reaction, a final analogy of sexual attraction with chemical processes may be found, if we are willing to trace the comparison without laying too much stress upon it. Consider the formula for the rapidity of the reaction, the different degrees of rapidity with which a sexual attraction between two individuals is established, and reflect how the value of “A” varies with the value of “t.” However, what Kant termed mathematical vanity must not tempt us to read into our equations complicated and difficult processes, the validity of which is uncertain. All that can be implied is simple enough; sensual desire increases with the time during which two individuals are in propinquity; if they were shut up together, it would develop if there were no repulsion, or practically no repulsion between them, in the fashion of some slow chemical process which takes much time before its result is visible. Such a case is the confidence with which it is said of a marriage arranged without love, “Love will come later; time will bring it.”
It is plain that too much stress must not be laid on the analogy between sexual affinity and purely chemical processes. None the less, I thought it illuminating to make the comparison. It is not yet quite clear if the sexual attraction is to be ranked with the “tropisms,” and the matter cannot be settled without going beyond mere sexuality to discuss the general problem of erotics. The phenomena of love require a different treatment, and I
