A woman’s genital apparatus is both internal and external. The external genitalia are called the vulva when they are referred to all together. The most obvious part of the vulva is the part we called the major (or sometimes outer) lips, which enfold the rest of the genitalia. If these lips are parted we see two smaller lips; these are called the minor lips and have a very high degree of sexual responsiveness. Even in books for laymen the Latin words are often used for these two organs: _labia majoris_ and _labia minoris_, which mean, simply enough, the major lips and the minor lips. The labia majoris also contain within their folds the rest of the external genital structure of woman. Here we find the clitoris, the vestibule, and the urethra, or opening to the bladder. The clitoris is by far the most important and most widely misunderstood part of the external genitalia. It lies immediately above the top fold of the labia minoris and is a little piece of tissue slightly less thick than a pencil. This organ is enormously important to the whole psychological and sexual development of the individual woman. It is often called the “homologue of the male penis,” and this simply means that in the embryo the cells which form the penis in the male are the same cells which form the clitoris in the female. Thus the two organs have the same cellular derivation. The clitoris, like the male penis, is made up of erectile tissue, and when a woman is sexually excited it becomes erect in the same manner that the penis does. It also has a head and a foreskin covering it, and the head of the clitoris, at least in children and adolescents, is generally extremely sensitive to stimulation. In the fully mature female this sensitivity often diminishes, giving way to the vagina as the primary source of the greatest sexual pleasure. However, many women who become fully mature sexually maintain much of the original sexual responsiveness of the clitoris. The remainder of the external genitalia is contained within the vestibule. This is the entrance proper to the vagina and is very susceptible to sexual excitation. The vestibule lies between the minor lips and is directly beneath the clitoris. It contains the hymen, the urethral opening, and the openings of the glands of Bartholin. The hymen is generally referred to as the maidenhead. It is a thin membrane which partly covers the entrance to the vagina. There is no direct sexual sensation on the hymen, and sometimes pain is experienced when it is perforated, usually during the first intercourse, although the hymen can be broken by an accident in childhood, through the insertion of surgical instruments, etc. Because of the pain associated with its perforation and the stories that a young girl often hears about this pain, it can be a source of much anxiety to her and condition her attitude toward sex in general.