In the last decennium, a certain change has taken place in this respect. A wave of sex discussion is sweeping over the civilized countries of the world. The former taboo on the discussion of sexual matters has been more or less removed and the veil lifted. Things which not very long ago could not have been mentioned in polite society except in whispers and with low breath, are now publicly discussed in season and out of season. As it is often the case, we have turned from the one extreme of complete darkness to the other extreme of too glaring light. Sex enlightenment runs rampant at present. It haunts the stage, lurks in innumerable societies and crops out in newspapers and magazines. But, although the world is full of sex discussion, the emphasis is generally laid upon sex-hygiene and upon the knowledge of the relations of the sex function to mental and physical development. Sex-hygiene is nowadays held to be a proper subject of pedagogy and is taught in many schools and colleges. But the emotion of Love is still very little studied, and it is still wrapped in complete darkness. A great deal of ignorance still prevails in regard to this important emotion. Few people understand under this much-abused word one and the same emotion. The same word is used to designate entirely different feelings. The ancient Greeks had three different words to express the different emotions that go under the name of love. One of the highest emotions is expressed by the word ἀγαπάω. It is the love man feels for God, parents or country. It is the love founded upon worship, adoration, gratitude and habit. The other kind of love was expressed by the word φιλέω. It designates the love founded on sympathy and liking, as the love of friends, of humanity, of wisdom. The last, amatory emotion, was expressed by the word ἐράω. It is the love founded upon sex-attraction. It is a purely instinctive emotion, found throughout the animal kingdom and even among some plants. Hence it is just the feeling which should not be treated with such besotted reverence. True enough sexual passion is the passion of creation, the most important function in the universe. Sympathy, affection, fidelity, sacrifice, indeed, all those noble traits, included under the term altruism, spring from the reproductive instinct. Still the two emotions, love, sung by poetry and exalted by art, and sex-attraction, found in animals and plants as well as in man, can not be identical. Still they are both generally confounded even by the best writers. To spread more light upon this important subject is the aim of this treatise. It has been written for the elucidation of the normal amatory emotions, considering the pathological changes only by way of contrast, for the perusal of the profession of medicine and of students of medical jurisprudence. FOOTNOTES: