These powerful contractions of the vagina, alternating rhythmically with the dilatations occurring during the orgasm, grip the glans penis tightly, and induce a coaptation of the male urethral orifice with the os uteri externum, and the enlargement of the latter orifice facilitates the entrance of the semen. According to O. Adler, sexual excitement of the woman during sexual intercourse begins with very powerful congestion of the entire reproductive apparatus, including even the fimbriæ surrounding the abdominal orifice of the Fallopian tubes; this congestion gives rise to an erection of these parts, and especially of the clitoris, the labia minora, and the vaginal wall. At the same time, the glands of the vaginal mucous membrane and of the vaginal inlet begin to secrete, as is manifest by the moistness of the external genital organs. There now begin gentle rhythmical contractions of the vagina and of the pelvic muscles, and during the orgasm these increase, to become spasmodic contractions, whereby an increased secretion is extruded, and more especially is there an evacuation of uterine mucus. It is very important to note the various physiological accompaniments of coitus, since they assist us to understand the mode of origin and the biological root of many sexual perversions. Already in normal sexual intercourse sadistic and masochistic phenomena may be observed. The biting and crying out mentioned by Roubaud as occurring in the voluptuous ecstasy are, indeed, of very frequent occurrence. Rudolf Bergh, the celebrated Danish dermatologist and physician, of the Copenhagen Hospital for Women suffering from Venereal Diseases, alludes regularly in his annual reports to the consequences of “erotic bites.” Amongst the Southern Slavs, the custom of “biting one another” is very general (Krauss). The intense dark red coloration of the face and of the reproductive organs and their environment is also a physiological accompaniment of sexual excitement, and this coloration is more marked in consequence of the associated turgescence of the male and female genital organs; it leads, moreover, to associations of feeling in which the =blood= plays a dominant part. Hence we deduce the biological and ethnological significance of the colour red in the sphere of sexuality. The nature of the sadist “to see red” during sexual intercourse is, therefore, firmly founded upon a physiological basis, and merely exhibits an increase of a normal phenomenon.[17] The crying and cursing in which many individuals find sexual gratification has also a physiological representative in the inarticulate noises and cries frequently expressed in normal intercourse. It is remarkable that an Indian writer on erotics--Vātsyāyana--deduces this verbal sadism from the various noises which are commonly made in normal intercourse. Similarly, in both parties to the sexual act the presence of masochistic elements can be detected: witness the patience with which pain is borne