Under the goad of imputed general inferiority, women have claimed not only political but also mental equality. It has seemed to them that nothing short of the full recognition by the dominant male of their mental capacity would bring to them the sense of worth and dignity before which the complex and its baleful effects would vanish. Unfortunately, whatever success they may have obtained in the realization of their political demands, the facts continue to be, or seem to be, against their claim of mental equality.

With regard to the past, they have found it sufficient to plead social disabilities as an explanation of their inferior performance in every or almost every form of activity. How could woman have attained eminence when the institutions of higher learning were closed to her, and when society in general refused to help her to gratify any of her ambitions if it led beyond the home?

Science, in the form of mental tests, has seemed to come to the support of this uncertain argument. No significant differences have been found to exist between schoolboys and schoolgirls or even between adult men and women. Unfortunately, the mental tests so far available are applicable to only certain parts of the mental life: the functions of the sense organs (acuity of perception, fineness of discrimination, and so forth), memory, certain forms of imagination, of comparison, of judgment, and some other aspects of what makes up 'intelligence.' No adequate test of the dynamic aspect of the mind that is, of interest, persistency, energy-has as yet been devised. When it is realized that the intellectual abilities are useless without motive power, the impossibility of deducing from the possession of equal

Unfortunately, again, for the peace of mind of women, the extensive removal of social disabilities, which has recently taken place, has not yielded the fruits expected by the believers in equality of mental ability. It is true that even now, in many professions and activities, women enjoy neither the encouragement nor the freedom given to men. Nevertheless, it may well seem to dispassionate observers that the degree of liberation gained by women during the last fifty years has not been followed by the fruits which equality of ability would have produced. Feminine musical composers and performers of the first rank are remarkably few, though public opinion and social customs place no obstacle in the way of the female musician.

Equality of opportunity and of intelligence can ensure equality of mental achievement only if energy also is equal. Are there reasons for referring to less mental energy the inferior performance of women? I think there are.

It is with trepidation that I engage in so delicate a venture as the demonstration of the inferiority of women in mental energy. Claiming a purely scientific interest in these matters would, I fear, not spare me a storm of protest. But may I not at least contend that the reference of women's deficiency to energy, and not to intelligence, constitutes a favorable change of venue? Is it not easier to confess to fatigue than to lack of wits? So it almost seems that success in this attempt means ridding womankind of the dreadful inferiority complex. They may, therefore, perhaps bear with me.

In any case, I trust to their fairness a trait which, I am glad to say, is not impugned in the following pages.

II

Differences in energy exist, of course, within the same sex. Let us, then, to begin with, seek a clear and somewhat detailed understanding of their effects as they manifest themselves in persons of the same sex.

Here are two college freshmen, Paul and Peter, whom we will suppose identical in intellectual excellence and in every other mental trait, energy only excepted. They are equal as to the quality of their mental abilities and dispositions, including their emotional make-up; they differ only in the quantity of the mental work they are able to perform. Let us assume that seven hours of college work leave Paul tired out, while Peter can do nine hours of the same work without more fatigue. What will be the consequences of this difference?

If both are average students and work just enough to pass the examinations, and if an average of seven hours' work a day is required for that purpose, then at the end of the day Paul will be tired out and therefore not inclined to further mental effort. His knowledge will remain, on the whole, limited to college studies. If he belongs to committees, to the editorial board of the college paper, or to any other extraacademic bodies, his services will not be of much value - he has too little energy left after doing his class-work.

Quite otherwise with Peter. He will have each day, on an average, two fruitful hours to devote to some pursuit other than the necessary class-work. He will be useful to college organizations to which he may belong. As simple member or as chairman of some of these, he will come by a variety of

information that Paul will not get. He will, in particular, learn to manage men, and will have an opportunity to develop the traits of the leader. The greater his knowledge and effectiveness, the more he will be in demand and the more competent he will continue to become. Should Peter have deep intellectual interests and, instead of doing merely the necessary academic work, should he devote his spare energy to the extension of his knowledge and training, a corresponding accumulation of efficiency would take place in that direction.

Four years of college life, with each day two additional hours of fruitful activity on the part of Peter, will produce such differences between him and Paul in actual achievement and in power of achievement that no one will regard them as intellectually equal. Even their teachers will get the impression that Peter is the possessor of far greater mental ability than Paul. He is, in fact, better informed and far more efficient; yet they began with intellectual talents of the very same quality.

The ascription of superior performance to superior intellectual endowment when it is due, in fact, to superior energy is one of the common confusions besetting a muddle-headed humanity. The much-performers in business, in politics, and even in the arts and sciences, are often ranked far above their true place in the scale of intellectual talents talents to observe, to remember, to understand, to appreciate, to reason. The very quality of their achievements conspires with their quantity to produce the deception. For quality also is improved by longsustained effort. In my student days, I boarded for a while in the same house with a young woman said to have a remarkable gift for the piano. Yet, as time passed, she seemed more and

Even in the fields of endeavor involving, as we say, purely mental work,mathematics, for instance, energy, and not only intellectual talent, determines the quality of achievement. Other things being equal, the person who in the attempted solution of a problem wearies last is the one who has the best chances of success. But the problem of the advantages due in this field to greater energy must not be considered with reference to a brief period of time. The energy-factor operates throughout life. The greater store of mathematical knowledge accumulated throughout his school and college years by the less easily fatigued person will give him such an advantage over his more easily tired competitor that now, even in the same space of time, he will readily surpass him, not in amount of work merely, but also in its quality: the problems he will be able to solve will be beyond the present attainments of the other. The world is full of men of vast achievements, reputed of transcendent intelligence, who owe their success to a surpassing energy actuating a mediocre brain. Not their intellectual talents but their ceaseless use of them is their distinction.

The student who in college understood with difficulty may astonish you by the place he takes in the community, while the brilliant youth who with little work was at the top of his class may never be heard from. Shall we say that the only advantage of the former over

the latter must be one of energy, of capacity to work longer hours? There are obviously other differences between people besides quality of intelligence and quantity of energy — as, for instance, the one indicated by the words 'interest,' 'curiosity,' and 'purpose.' Since we are concerned merely with difference of energy when everything else is identical, it is quite sufficient for our discussion to note that the duration of interest, of curiosity, and of purpose wanes with the coming-on of fatigue. The duration of labor to which these incentives prompt at any particular moment is therefore limited by the energy at one's disposal.

We may, then, say that, other things being equal, the greater the difference in energy, the greater the difference in mental achievements, both in quantity and in quality. The inferiority in the mental performance of women, however great it may be in quantity or quality, can therefore be explained without the assumption of inferior intelligence.

III

A direct and measured knowledge of energy-difference between the sexes is not altogether lacking. It is well known that, in so far as muscular power and endurance are concerned, woman is, on the average, markedly inferior to man. This difference cannot possibly be referred to any form of social disability, for it exists among savages, where physical labor is not denied to the sex; it exists in the apes; it exists even in all the species of the mammalian class to which man belongs. It has been affirmed, furthermore, that at the same weight woman is inferior to man by about thirty per cent. We are

1 Professor A. V. Hill, in his address as President of the Physiology Section of the British Association for the Advancement of Science, in 1925.

dealing here undeniably with a sexlinked difference.

The lesser muscular performance of women when compared with men of the same weight may mean that in the former a smaller part of the total weight is in muscle. In that case, at the same total bodily weight women's muscles would be smaller than those of men. We know, as a matter of fact, that this is so. Woman is handicapped in athletics, not only by her smaller size, this is not, it is true, always a handicap, but also by the weight of organs peculiar to her sex. Whether that handicap accounts for the whole of the thirty-per-cent difference is a question which, as far as we know, remains for the physiologist to answer.

But what have these facts and considerations to do here? Our problem does not refer to muscular performance, but to success in the professions, the arts, the sciences. Well, muscular and mental fatigue are not so independent of each other as the words might lead one to think. It is well known that physical fatigue incapacitates one for mental work, and also that mental fatigue incapacitates one for physical work.

The truth of the first statement is fairly obvious. Movements result from the enervation of muscles- that is, muscles act only in so far as nervous energy is brought to them and is consumed by them.

The second statement- that mental fatigue incapacitates for physical work

is perhaps less obviously true. However, hard students and intellectual workers verify the truth of it every day. Eight hours of intellectual effort are usually enough to exhaust most of one's muscular energy.

Do we, then, think with our muscles? The psychologist does not put it that way. He affirms, however, that muscle activity is involved in the performances

we have called mental. Music, painting, sculpture, make large calls upon physical endurance, particularly during the learning-period. To this we have already had occasion to refer in the case of piano-playing. It is sometimes said that the business man gets no exercise at his work. He undoubtedly exercises certain muscles. He sits up in his chair; he stands; he walks about, gesticulates, talks. All these activities mean muscle contractions, and general muscular fatigue when the evening

comes.

The muscular activity in so-called intellectual work is not limited to the muscles necessarily involved in pressing down the keys of a piano, in using the pen, in speech movements; it spreads more or less to every muscle. Even when we do, as we say, nothing more than think, there are muscular contractions going on all over the body. Not a single one of the external muscles is entirely relaxed; and anyone may ascertain, by paying attention to the muscles of his face, of his arms, and of his legs when in the midst of a difficult train of thought, that many muscles are in a state of high tension. The fatigue produced by mental effort is, then, far from independent of muscular fatigue.

of internal secretion, — thyroid, pituitary, pineal, thymus, adrenal, pancreas, and so on, glands whose secretions are poured out, not outside the body, but into certain organs or into the blood stream, have established the stimulating effect of certain of them and the depressing effect of others.

Fatigue depends, however, as already said, not only upon the supply of energy, but also upon the action of the organs involved in the elimination of the tissue-waste resulting from work. If not rapidly removed, these waste products clog the whole machinery. Here we are to think mainly of the excretory functions of the intestines and the kidneys, and of the oxidizing processes in respiration.

If women differ from men in energy, it need not be, therefore, because of a difference in the number or size or quality of the brain nerve-cells; it may be because of differences in the endocrine glands or in the organs concerned with the elimination of the waste products. An account of the functions of the glands of inner secretion, however incomplete our knowledge still is, throws a new and fascinating light upon human nature, and seems to place in the hands of man means of self-transformation rivaling the magic of the Arabian Nights. Yet only the briefest and barest of remarks are possible here.

Among the best established of the discoveries just referred to is that 'the energy quantum of an individual is a function of, and is determined by, his thyroid gland," a gland situated in the neck, near the windpipe. Insufficient thyroxin means inactivity, poor memory, and other intellectual weaknesses. A normal-minded person overtaken by that disease weakens mentally and, if the disorder is severe, becomes idiotic. Louis Berman, The Glands Regulating Personality, 1921.

If extract of thyroid is fed to him, he recovers rapidly. There are sufficient reasons to think that in a case of this sort the changes which take place in the brain the mechanism of the mental life do not destroy it, but make it merely unserviceable. It is as when water gets into the carburetor of an automobile. As soon as the water is removed, the machine works as well as ever; the carburetor had not been destroyed, but it could not be used.

The secretion of the thymus gland - in the chest, about the windpipe produces, on the contrary, an extraordinary proneness to fatigue. Sturdily muscled individuals too much endowed with thymus succumb to an amount of work easily done by persons with smaller muscles. The fatiguableness and endurance of muscle may thus be traced, we are told, to the overaction or underaction of endocrine glands.

Not only the muscle but the brain activity itself is controlled by some of these secretions: 'Acuteness of perception, memory, logical thought, imagination, conception, emotional expression or inhibition . . . are influenced by the internal secretions.' They dominate the activity of the molecules and atoms of the nerve cells, increase or decrease the conductivity of the nerve fibres, and so forth. The expression of emotion, the instincts, and suggestibility are said to be subject to the action of certain of these secretions.

If great differences exist within the same sex regarding these secretions, still greater differences characterize the sexes, and these are the differences which interest us most. With male puberty there comes an increased activity of the anterior pituitary, while with female puberty an augmentation of the activity of the posterior pituitary takes place. The anterior pituitary is connected, not only with the male sex-functions, but