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 shall return to them in the second part of this book. None the less, there are analogies that cannot be denied when human attractions and chemotropism are compared. I may refer as an instance to the relation between Edward and Ottilie in Goethe’s “Wahlverwandtschaften.”
Mention of Goethe’s romance leads naturally to a discussion of the marriage problem, and I may here give a few of the practical inferences which would seem to follow from the theoretical considerations of this chapter. It is clear that a natural law, not dissimilar to other natural laws, exists with regard to sexual attraction; this law shows that, whilst innumerable gradations of sexuality exist, there always may be found pairs of beings the members of which are almost perfectly adapted to one another. So far, marriage has its justification, and, from the standpoint of biology, free love is condemned. Monogamy, however, is a more difficult problem, the solution of which involves other considerations, such as periodicity, to which I shall refer later, and the change of the sexual taste with advancing years.
A second conclusion may be derived from heterostylism, especially with reference to the fact that “illegitimate fertilisation” almost invariably produces less fertile offspring. This leads to the consideration that amongst other forms of life the strongest and healthiest offspring will result from unions in which there is the maximum of sexual suitability. As the old saying has it, “love-children” turn out to be the finest, strongest, and most vigorous of human beings. Those who are interested in the improvement of mankind must therefore, on purely hygienic grounds, oppose the ordinary mercenary marriages of convenience.
It is more than probable that the law of sexual attraction may yield useful results when applied to the breeding of animals. More attention will have to be given to the secondary sexual characters of the animals which it is proposed to mate. The artificial methods made use of to secure the serving of mares by stallions unattractive to them do not always fail, but are followed by indifferent results. Probably an obvious result of the use of a substituted stallion in impregnating a mare is the extreme nervousness of the progeny, which must be treated with bromide and other drugs. So, also, the degeneration of modern Jews may be traced in part to the fact that amongst them marriages for other reasons than love are specially common.