Part 16

This other soul, below the animal, Bloating and coating body’s baser parts With the manure of its desires and arts, Helps flesh to grow still more corporeal.

I pray that I may still inhabit earth, Where grass invites the foot, and roses smell; Yet shall I lead my body on to dwell In the eternal land of second birth, If, nought contemned, each part of being’s whole Is taken up in my transmuting soul.

SEX BIOLOGY AND SEX PSYCHOLOGY

“And now I see with eye serene The very pulse of the machine.” --W. WORDSWORTH.

“There is reason to believe that the processes which underlie all great work in art, literature, or science take place unconsciously, or at least unwittingly. It is an interesting question to ask whence comes the energy of which this work is the expression. There are two chief possibilities: one, that it is derived from the instinctive tendencies which, through the action of controlling forces, fail to find their natural outlet; the other, that the energy so arising is increased in amount through the conflict between controlled and controlling forces.”--W. H. RIVERS.

The biology of sex is a vast subject. Not only are there questions of sex-determination, but the whole sexual selection problem has to be considered, together with the evolutionary function of sex, and its first origin. I can only attempt, in the short space at my disposal, to deal with one or two of the chief points, and only in so far as they bear on questions of human sex psychology.

In the first place, then, we have to consider the evolutionary history of sex. Of its origin we can say only that it is veiled in complete obscurity. Once present, however, it appears to have a definite function by making possible, through sexual reproduction, all the various combinations of any heritable variations that may arise in different individuals of a species, and so conferring greater evolutionary plasticity on the species as a whole.

Primarily, sex implies only the fusion of nuclei from two separate individuals; there is no need for sex differences to exist at all. Sex differences, however, are almost universal in sexually-reproducing organisms, and represent a division of labour between the active male cell and the passive female cell, the former taking over the task of uniting the two, the latter storing up nutriment for the new individual that will result from that union.

The subsequent history of sex is, roughly speaking, the history of its invasion of more and more of the organization of its possessors. First the male as a whole, and not merely its reproductive cells, tends to become organized for finding the female. The female’s whole type of metabolism is altered to produce the most efficient storage of reserve material in her ova, and later she almost invariably protects and nourishes the young during the first part of their development, either within or without her own body. Appropriate instincts are of course developed in both male and female.

At the outset there is enormous waste incurred in the liberation of sperms and ova into the water, there to unite as best they may. Congress of the sexes eliminates the major part of this waste, and is universal above a certain level. This is in itself the basis for other changes. As the mind, or shall we say the psycho-neural organization, becomes more complex, the sexual instinct becomes more interwoven with the general emotional state; and a large number of animals appear not to mate unless their emotional state has been raised to a certain level. The result of this is that special actions, associated generally with bright colours or striking structures, with song or with scent, come into being.

The exact mechanism of the appearance of these courtship-displays is a much-vexed point; but it is undoubted that they only occur in animals with congress of the sexes and with minds above a certain level of complexity, and that they are employed in ceremonies between the two sexes at mating-time. There can subsist no reasonable doubt that there exists some causal connection between the associated facts.

An important point, which has been commonly overlooked, is that such characters and actions may be either developed in one sex only, or in both. In a large number of birds, such as egrets, grebes, cranes, and many others, the courtship-displays are mutual, and the characters used in them developed to a similar extent in both sexes. Such characters are therefore often not secondary sexual differences, and we had best use Poulton’s term epigamic for them, whether they are developed in one or in both sexes.

The human species, in accordance with its complexity and flexibility of brain, has epigamic characters of both kinds. Some, like voice and moustache, are different in the two sexes, others, such as colour of eyes and lips, the hairlessness of the body and grace of limbs and carriage, are common to both.

In the vertebrate stock, two main lines of evolution as regards sexual relationships may be traced. The first is predominant in mammals: here, in most species, the female will not receive the male except at fixed times, which are determined by a purely physiological mechanism, the internal secretion of the gonad (reproductive organ). Here we consequently find that the rule is for the males to fight for the possession of the females, not to display before them. In the monkeys, presumably as a result of a lessened dependence of mental upon physiological processes, bright colours and special adornments of various parts of the body are frequently developed.

In the birds, on the other hand, although here too the internal secretion of the gonad delimits a period in which alone congress of the sexes can occur, it does not act for such a sharply-limited time as in the mammal, nor is it so intense as completely to override other components of the mind. As a result, general emotional stimulus may play an important part in inducing readiness to pair, and we accordingly find display of some sort, either by the male alone or by both sexes, present in the great majority of species. It is at least partly in correlation with this that beauty of voice and brilliant appearance is far commoner in birds than in mammals.

The monkeys represent in some way a transitional stage towards that seen in man, in whom the conditions have come to resemble those found in birds, with consequent great development of epigamic characters and actions of one sort and another, both physical and mental. Thus we see that sex, after invading and altering the conformation of the body, finally invades and alters the conformation of the mind.

As regards the other great biological question, of the determination of sex, a very few words will suffice. In the first place I have no time to consider plants or lower animals. In almost all higher animals that have been investigated, however, there has been found some hereditary mechanism for ensuring a rough constancy of sex-ratio. This mechanism resides in the so-called chromosomes of the nucleus. These exist for the most part in similar pairs in both sexes: but one pair is dissimilar in one sex. In mammals and man this sex is the male. Man possesses one chromosome less than woman. He possesses only one member of this pair of special sex-chromosomes, whereas she possesses two. All her ova are alike in possessing one, whereas half his sperms possess one, half possess none. Therefore, when the former kind of sperms fertilize an ovum, two sex-chromosomes are present in the fertilized egg and a female results; when the latter, only one, and the offspring is male.

Putting the matter in the broadest terms, we can say that there is a different balance of hereditary factors in male and female, and that this difference of balance dates from the moment of fertilization, and normally determines sex.

Various agencies may alter the balance. The chromosomes themselves may vary in what we must vaguely call their potency; or external agencies may affect it. As a result, we sometimes obtain strange abnormal individuals, in which the balance has been upset; in them development results sometimes in organisms permanently intermediate between male and female, sometimes in a change of sex at some period of development.

In insects the chromosomes appear to be predominant throughout life. In vertebrates, however, they seem to play their chief rôle in early development, ending by building up either a male or a female gonad in the early embryo. This, once produced, takes over what remains of the task of sex-determination. It secretes a specific internal secretion which in a male acts so as to encourage the growth of male organs and instincts, to suppress those of females; and vice versa in a female.

As a result of this difference we find that castration in insects, even followed by engrafting of a gonad of opposite sex, produces no effect upon other sexual characters; whereas it exerts a profound effect upon mammals or birds.

As a second result, we find that in vertebrates the gonads form part of what has been called the chemical directorate of the body--the interlocking system of endocrine glands, each of which is exerting an effect upon the rest. The importance of this is seen in the experiments of Steinach, Sand, Voronoff, and others, who have been able to obtain a rejuvenating effect in senile mammals by increasing, by various methods, the amount of secreting reproductive organ in the body.

To what then has our rapid survey led us? The actual origin of sex is lost to us in the mists of a time inconceivably remote. Its preservation once in existence, and its present all-but-universal distribution seem to be definitely associated with the biological advantage of the plasticity which it confers. Later, the primary difference between male and female--their power of producing different sorts of reproductive cells--leads on to secondary differences. These differences may be biologically speaking non-significant, mere accidents of the primary difference. Or they may be in the nature of a division of labour between the sexes, this division of labour usually concerning the protection of the embryo or the care of the young, or more rarely the preservation of the individual itself. Or, finally, they may concern the more efficient union of the gametes; such differences may merely affect the ducts and apertures of the reproductive system, and be more or less mechanical; or they may concern the use of these systems, in the form of still mechanical instincts, or they may be concerned in some way or other with the emotional side of the animals, and consist in characters and actions which stimulate the emotions of the other sex, characters which we have termed epigamic.

It is only in higher groups that these emotion-stimulating sexual characters arise, for only in them has mind reached a sufficient degree of perfection. But even though detailed study reveals in a bird or a mammal a mental life of a complexity far more considerable than the average man would imagine, yet on the whole it is straightforward and its currents run fairly direct from stimulus to fulfilment.

When we reach man, however, the whole aspect of the matter changes. The change is most marked, naturally, in his mental organization. Through his powers of rapid and unlimited association, any one part of his experience can be combined with any other; through his powers of generalizing and of giving names to things, his experience is far more highly organized than that of any animal; through speech and writing he is inheritor of a continuous tradition which enormously enlarges his range of experience. Again, he can frame a purpose and thus put the objective of his actions far further into the future than can lower organisms.

There are, however, also changes of considerable biological importance on the physical side. Man brings with him from his animal ancestors the endocrine secretory mechanism of the reproductive organs: but his life is not subordinated to it in such an iron-bound way. To start with he has gradually lost all semblance of a breeding-season. Traces of it survive in some primitive races, but in civilized communities all one can say is that the number of births may show a slight seasonal variation; and the reproductive organs are capable of function in all twelve months of the year--a state of affairs known, I believe, in no other vertebrate, or at least in no wild species.

In the second place, there has been in the female a further emancipation of the sexual life. In all other mammals the female will only receive the male at certain well-defined periods, which in their turn depend on cyclical changes in the ovaries. In man this restriction has been overcome, and, in spite of the survival of a certain degree of cyclical change in feeling, neither sex is restricted any longer to certain physically-determined periods for the consummation of its sexual life. This is, we may say, a triumph of mind over matter in the human organism, of the mental elements of the sexual life over the purely physical elements.

This is not to deny that the sexual life of man is dependent upon the reproductive hormones. It is apparently necessary for proper activation of the sexual centres in the brain that there should occur a continuous liberation of secretion from the reproductive organs into the blood. Again, the mental activities of man are so much more important than those of other forms that even the cessation of activity of the reproductive organs, for instance in the female at the change of life, or even their total removal, need not prevent the continuation, albeit in a modified form, of the sexual life in its varied indirect manifestations.