The subject of love is always of the most absorbing interest to the younger and more active portion of a people; sexual passion, in its ennobling or debasing form, exercises irresistible attraction.

Our amusements and our customs are largely moulded by the same powerful attraction, viz., the mental and moral quality of the relations which are formed between the sexes. As civilization advances, and dense masses of human beings are crowded together in heterogeneous selfish strife, the destructive extremes of luxury and pauperism appear. From this state of society, where misery will do anything for money, and the satiety of luxury seeks fresh stimulus, speculation in this strongest part of our nature—sex—arises. Its creative use disappears, and it becomes a subject of merchandise. Every variety of effort is made to stimulate and debase the mental quality or sentiment of sex, and the strength of human passion furnishes an exhaustless field for corrupt speculation.

It is therefore not the simple physical aspect of the reproductive powers which is remarkable in humanity. The physical instinct is shared with the rest of the animal creation. It is the unique and powerful mental and moral element, the principle that moulds and governs human sex, which produces such striking results in the life of our race.

The mental or emotional element in these powers, both in relation to the action and reaction of mind and body, and the hereditary transmission of tendencies, will, therefore, largely engage the attention of the physiologist who truly studies our human nature. The distinctive moral character of human sex renders the exclusive study of physical phenomena in man as useless and unscientific a method of investigation as would be the study of music on dumb instruments. The distinctively mental character of human sex must therefore always be recognised as a guide in any physiological inquiry into the structure and functions of the physical organs especially appropriated to the use of sex.

The clue to a true knowledge of sexual functions in man and woman is found in this striking peculiarity of the human race, viz., that these functions are largely dominated by mental action, and that sex in the human being does not mean simply the action of the physical organs, but also the conjoined mental principle directing those organs.

Sex, therefore, in the human race alone, resting upon that broad, well-marked mental foundation, is capable of great development towards good or towards evil. As simply material satisfaction soon reaches the limit which bounds matter, so mental or spiritual enjoyment is capable of indefinite growth. It is this mental sentiment peculiar to human sex which is capable of a twofold development. It may grow into a noble sympathy, self-sacrifice, reverence, and joy, which enlarge and intensify the nature through the gradual expansion of the inborn moral elements of sex. It is also this same intensity of the mental form and power of sex, possessed by mankind alone, which allows of the perversion and extreme degradation of sex which is observable only in the human race. It is the degradation of this mental power when running riot in unchecked license that converts men and women into selfish and cruel devils—monsters, quite without parallel in the brute creation.

These facts are strikingly illustrated by the anatomical and physiological constitution of the human being. The structure and functions of the generative system in our race are contrived in such a way as to support two great leading principles of existence.

These fundamental principles are—First, the independence, freedom, and perfection of the individual. Second, the preservation of the race. These two objects are secured to a certain extent in all highly organized creatures; but in the human race provision is made for individual freedom in a much more marked and perfect manner, in accordance with the superior rank of man in creation.

The brute, both male and female, is at certain times blindly dominated by the physical impulse of sex. This impulse in the lower animal is a simple imperative instinct, unhesitatingly yielded to, with no preparation or after-thought, with no calculation, shame, triumph, or regret. But it is very different with the human race, as it grows from lower to higher states of society. Thoughts and feelings, social ties and conscience, religious training and the objects of life, all act upon the distinctive mental character of sex; and it is seen that the welfare of a third factor, viz., the child, is inseparably connected with these relations.

Its character is thus changed to a very complex faculty. The young man or woman blindly yielding to this power of sexual attraction, against the remonstrance of a high sense of duty, is torn by remorse, and is consciously self-degraded.