Chapter III – The Seminal Fluid and the Mechanism of Erection. Exactly that is discussed. Nocturnal emissions are normal, to a point. If you’re having them more than once a week, that means the organ is too relaxed, presumably because you masturbate or have sex too much. He allows that women also can have these sorts of “wet dreams;” however, unless it’s during sex, any orgasmic event a woman has is unhealthy.
Sometimes, men are secreting other fluids that they are led to believe are seminal fluid. Why does this happen? The magic word: masturbation. If mucus is coming from the urethra, it means you’ve been having too much sex under the influence of alcohol.
From here, the doctor moves on to the nerve centers of the body that control the erections. He talks at length about the cerebellum, and what happens when it’s removed. If there are tumors or blood clots in it, it causes nymphomania. The size of the cerebellum does not correlate with the size of one’s sexual appetite, however.
To conclude the chapter, he compares blushing to erection. A rush of blood to the “head,” indeed.