"Thus, Havelock Ellis, after various attempts to explain sensual pleasure, again concluded that the impulse which leads to pleasure is, in a certain way, independent of the seminal glands and their condition. From a physio-anatomical point of view, the existence of sexual centers in the brain (already presumed by Gall) as well as in the spine and in the sympathetic nervous system is now generally accepted; this is the counterpart of the essential role played by the imagination not only in love generally but in sexuality itself, for the imagination accompanies and sometimes even starts and activates the whole process of copulation, whereas at other times it can stop it irreversibly."

I wonder where we are at with this now?