Sexual desire during the years of s**ual maturity is a phiysiological law. The duration of the pliysiological processes in the s**ual organs, as well as the strength of the s**ual desire manifested, vary, both in individuals and in races. Race, climate, heredity and social circumstances have a very decided influence lipon it. The greater sensuality of southern races as compared with the s**ual needs of those of the north is well known. Sexual development in the inhabitants of tropical climes takes place much earlier than in those of more northern regions. In women of northern countries Ovulation, recognisable in the development of the body and the occurrence of a periodical flow of blood from the genitals (menstruation), usually begins about the thirteenth to the fifteenth year; in men puberty, recognisable in the deepening of the voice, the appearance of hair on the face and mons veneris, and the occasional occurence of pollutions, etc., takes place about the fifteenth year. In the inhabitants of tropical countries, however, s**ual development obtains several years earlier in women — sometimes as early as the eighth year.
It is worthy of remark tliat girls who live in cities develop about a year earlier than girls living in the country, and that the larger the town the earlier, ceteris partium, the development takes place. Heredity, however, has no small influence on libido and s**ual power. Thus there are families in which, with great physical strength and longevity, great libidoand virility are preserved until a great age, while in other families the vita s**ualis develops late and is early extinguished.
In woman the period of activity of the reproductive glands is shorter than in man, in whom s**ual power may last until a great age; Ovulation ceases about thirty years after puberty. The period of waning activity of the ovaries is ealled the change of life (climacterium, meno-
pause). This biological phase does not represent merely a cessation of functional potency and final atrophy of the reproductive organs, but a transformation of the whole organism.
... The existencc of the s**ual instinct is continuous during the time of s**ual life, but it varies in intensity. Under physiological conditions it is never periodical in the human male, as it is in animals; it manifests an organic variation of intensity in consonance with the collection and expenditure of semen. In women the degree of s**ual desire coincides with the process of Ovulation in such a way that libido s**ualis is intensified after the menstrual period.
Sexual instinct — as emotion, idea and impulse — is a function of the cerebral codex. Thus far no definite region of the cortex has been proved to be exclusively the seat of s**ual sensations and impulses. This psychos**ual centre is nothing more than a junction and crossing of principal paths which lead on the one hand to the sensitive motor apparatus of the s**ual organs, and on the other hand to those nerve centres of the visual and olfactorv organs which are the carriers of that consciousness which distinguishes between the "male" and the "female".
The development of s**ual life has its beginning in the organic sensations which arise from the maturing reproductive glands. These
excite the attention of the individual. Reading and the experiences of every-day life (which, unfortunately, are now-a-days too early and too frequently suggestive), convert these notions into clear ideas, which are accentuated by organic sensations of a pleasurable character. With
this accentuation of erotic ideas through lustful feelings, an impulse to induce them is developed (s**ual desire). Thus there is established a mutual dependence between the cerebral cortex (as the place of origin of sensations and ideas), and the reproductive organs. The latter, by
reason of physiological processes (hypenemia, secretion of semen, Ovulation), give rise to s**ual ideas, images, and impulses.