This section is from the book "Human Sexuality", by J. Richardson Parke. Also available from Amazon: Human Sexuality.
No matter what its immediate precipitating cause, if conjugal congeniality lie at the bottom of a marriage, it is bound to turn out all right; and no matter under what roseate auspices of romanticism, and so-called love-at-first-Bight, it may be entered into, if this congeniality be wanting, it is bound to turn out all wrong. It is so easy for a young lady to imagine herself in love, when she only dreads becoming an "old maid;" to confuse love of the man with love of men, or of money, or home, or social position; and so hard to dissociate it from selfishness and adventitious circumstances, or to recognize even the existence, as a reality, of that pure, holy and disinterested love which comes only of a perfect union both of soul and body.
And on the other hand—indeed far oftcner—a man feels and believes himself in love every time he experiences the craving of his sexual instinct, without the remotest realization of the deeper and holier meaning of the word; and not unfrequently marries in such a mesmeric trance, only to be awakened, most disagreeably, by the voice of the judge, perhaps, assessing the amount of alimony.
How common it is for women, when they hear of some unfortunate case of seduction, to cry—" poor soul, she couldn't help it I She loved him boI" If I could speak directly to the ladies I should tell them there is no love in such cases. It is a mock article, mesmerism, hypnotism if you like, and if it satisfy your consciences to give it such euphemistic names; but, my candid opinion is, it is nothing but a very natural sexual desire which has simply failed in its purpose to escape detection.
So when a moping, haggard wretch throws himself into the river, because Mary Jane has refused him, and when Mary Jane herself loses her appetite, begins to indite love ditties, and pines away in seclusion, be assured it is not true love. True love doesn't do such things. They are done only by the morbid, neurotic, diseased temperament, the unconscious victim of sexual hyperesthesia., who mistakes his own infirmities for an emotion he is probably quite incapable of ever feeling or conceiving; and who proves his ignorance of the true concept of love by inflicting pain upon himself, rather than pleasure upon the object of his passion.
But, to analyze the question more closely, the stimulating impressions produced upon us by health, youth, beauty, symmetry of form, ornamentation, or other species of attraction, are all elements of sexual feeling. The repugnance which every man feels for sexual intercourse with a woman of another race, possessed naturally of a different standard of physical beauty, and, possibly, a different degree of desire, as well as his instinctive horror of incest, or of intercourse with animals, belongs to the same class of sexual phenomena. Around this passion, as a fundamental element, are grouped such a host of subjective feelings as would fill a whole volume in their analysis; but it is only to the most prominent of these that I shall ask the reader's attention for the present.
 
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sexuality, reporduction, genitals, love, female, humans, passion