This section is from the book "Human Sexuality", by J. Richardson Parke. Also available from Amazon: Human Sexuality.
In the former case, the psychological element would be subordinated to purely physiological processes; and, indeed, it would not be difficult to show that evacuation of long suppressed secretions, either physiological or pathological, especially in youth, is accompanied by a degree of pleasure almost equally intense with that of the sexual discharge; although in adult-life, such sensations are feebler, from habits of restrictive training, and from being pushed into the background of consciousness, through greater powers of volition, and the less imperious activity of the involuntary muscular system.
The "evacuation theory" of the sexual instinct was quite uniformly received up to the latter part of the nineteenth century; and grew chiefly out of the fact that the crude mind expresses itself in crude, language. Even yet the French call the brothel a privy—le doaoue;* and the medieval writers who alluded to woman as "a temple built over a sewer," did so from the same coarse concept of the sexual function.
Even Montaigne, paragon of literary politeness, contributed to this popular view respecting it; remarking that "Venus (venery), after all, is nothing more than the pleasure of discharging our vessels, just as nature renders pleasurable the discharges from other parts;" and the delightful author of Utopia' speaks naively of the pleasure experienced "when we do our natural easement, or when we be doing the act of generation."
"The genesic need," writes Féré (incorrectly, since he does not take into account how often desire for children, the unselfish impulse to give pleasure to another, the frequency with which the act is performed without need of evacuation, and many other conditions, may underlie the sexual act) "may be considered as a need of evacuation; and the choice is determined by the excitations which render the evacuations more agreeable."
 
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