It signifies partial or total absence of sexual feeling, i. e., impotence of voluptas. It also comprises all other kinds of impotency, as impotence of libido or of copulation. III. HYPERAESTHESIA. It signifies the abnormal intensity of the sexual desire and impulse, 1) Mixoscopy, 2) Erotomania, 3) Satyriasis, 4) Nymphomania, 5) Masturbation, 6) Incest. IV. PARAESTHESIA. It covers all possible forms of perversion of sexual feeling and sexual activity. A) Heterosexuality: Inclination to persons of the opposite sex, but with perverse activity. 1) Masochism, 2) Sadism, 3) Fetichism, 4) Exhibitionism. B) Homosexuality: The sexual feeling is directed toward the same sex. a) Perversity, 1) out of lust, 2) as a profession, 3) through necessity, 4) out of fear, b) Perversion, 1) psychical hermaphrodism, 2) strict homosexuality, 3) effemination or viraginity, 4) transvestism. C) Bestiality: The sexual feelings are directed in conjugium cum animalibus. _Paradoxia._—Paradoxia signifies the sexual activity in individuals who should normally present no sexual manifestations. The occurrence of sexual excitement at an age when the individual should ordinarily be without it belongs to this part of the pathology of sexuality. The continuance of the same degree of sexual desire in very old men or in women after the climacterium, as it existed before, is certainly unusual; yet it cannot be called pathological. The occurrence of pregnancies in wives of very old men and in women after the climacteric period proves that the ovaries continue to secrete ova even after menstruation has ceased, and that the testicles do not cease producing spermatozoa even beyond the limit of three scores and ten. Now, the sexual desire depends more upon the activity of the sexual glands than upon the physiological changes in the nervous apparatus of the generative organs in men or upon any changes in the uterus, which is only a repository for the development of the foetus. Hence the absence of erection in men or of menstruation in women does not necessarily imply absence of sexual desire. The appearance of sexual desire in boys before puberty and in girls long before menstruation has set in is also, as yet, within the limits of the normal; it becomes pathological only when the sexual desire is manifested in infants or very small children. Complete sexual development has been witnessed in children as early as the second year. The precocity of development in the organs of generation is usually accompanied by corresponding precocity in sexual desire.