So, then, let the reader of these lines, first, get a correct _mental attitude_ toward what is about to be said. Banish all prurient curiosity, put aside all thought of shame or shock, (these two will be hardest for young women to overcome, because of their training in false modesty and prudishness) and endeavor to approach the subject in a reverent, open-eyed, conscientious spirit, as one who wishes, above everything else, to know the honest truth in these most essential matters that pertain to human life. Get into this frame of mind, and _keep in it_, and what is here written will be read with both pleasure and profit. Once more, for we must make haste slowly in these delicate affairs, if the reader should find himself or herself unduly excited, or perhaps shocked, while reading some parts of what is here written, so that the heart beats too fast, or the hand trembles, it may be well to suspend the reading for a time, divert the mind into other channels for a while, and resume the reading after one has regained poise and mastery of one's self. That is, "_keep your head_" while you read these lessons, and you will be all right. IV THE SEX ORGANS And now, having given these cautionary directions, the way is clear for the making of definite statements and the giving of positive instruction. Here, then, is a brief description of the sex organs in man and woman. At first, only the names of the parts will be given, with such slight comments and explanations as are necessary for making this part of the subject clear. A detailed setting forth of the functions and proper exercise of these organs will be given later. The sex organs in a male human being consists, broadly speaking, of the penis and the testicles. All these are located at the base of the abdomen, between the thighs and on the forward part of the body. The penis is a fleshy, muscular organ, filled with most sensitive nerves, and blood vessels that are capable of extension to a much greater degree than any of their similars in other parts of the body. In a quiescent, or unexcited condition, in the average man, this organ is from three to four inches long and about an inch or more in diameter. It hangs limp and pendent in this state, retired and in evidence not at all. In its excited, or tumescent condition (the word tumescent means swelled, and is the technical word for describing the erect condition of the penis) it becomes enlarged and rigid, its size in this state being, on an average, six or seven inches long, and from an inch-and-a-half to two inches in diameter. It is almost perfectly cylindrical, slightly thicker at the base than at its forward part.