This section is from the book "Human Sexuality", by J. Richardson Parke. Also available from Amazon: Human Sexuality.
It was from the peculiar character of the Austrian novelist, Sacher-Masoch, who first discovered his perversion by the pleasure he experienced in being kicked in the face by his mistress, that Krafft-Ebing was led to adopt the term masochism, as the counterpart of sadism; but, as I have previously remarked, a careful consideration of the phenomena of both conditions will lead us to discard even an imaginary line of demarcation. De Sade, himself, was not a pure sadist, any more than Sacher-Masoch was a pure masochist, the sexual algophily of which Fere speaks1 being equally applicable in both cases; and the term algolagnia*—pain with sexual excitement—which Schrenk-Notzing invented to cover both sadism and masochism, seems fairly adequate to describe both the passive and active forms of the perversion.
I am not sure that I am absolutely correct, indeed, in applying the term abnormal to either of these perversions; the instinct to bite, for instance, in sexual excitement being so universal as to fall readily within the lines of normality; and it is only when we go beyond this, and into the more pronounced forms of instinctive cruelty, that the adopted classification appears justified. The impulse of furibund passion, as manifested in the love-bite, may or may not be to shed blood; if it be the latter, and not the mere emotional outburst of sexual detumescence, common to all animals, it is a perfectly natural manifestation of the law which makes courtship only a modified form of combat, of which blood is the natural concomitant.
 
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sexuality, reporduction, genitals, love, female, humans, passion