7. Until twenty-one years of age the semen is unproductive, afterwards it becomes fertile, though boys and girls produce small and imperfect children: this is also the case with other animals. Young girls conceive more readily, but after conception suffer more in parturition, and their bodies frequently become imperfect. Men of violent passions, and women that have borne many children, grow old more rapidly than others; nor does there appear to be any increase after they have borne three children. Women of violent sexual desires become more temperate after they have borne several children. 8. Women who have attained thrice seven years are well adapted for child-bearing, and men also are capable of becoming parents. Thin seminal fluid is barren. That which is lumpy begets males; what is thin and not clotted, females. The beard also appears on the chin of men at the same period. CHAPTER II. 1. The catamenia appear when the moon is on the wane, from which some persons would argue that the moon is a female, for the purification of women and the waning of the moon occur together, and repletion occurs again in both after the purification and waning. In few women the catamenia occur every month, but in most at every third month. Those in whom they continue for only two or three days escape with ease: it is more difficult for those in whom it continues for a longer time, for they suffer during the whole period. In some the purification takes place all at once, in others by degrees; in all, however, the pain is considerable as long as they are present. In many women, when the catamenia are nearly ready to appear, the womb suffers so much from strangulation and disturbance, until they are discharged. 2. Conception naturally takes place immediately after this discharge in women, and those who do not then conceive, are usually barren. Some women, however, who have never menstruated, conceive. Such persons contain in themselves as much of the fluid as is usually left behind after the purification, but not so much as to make its appearance externally. Some women in whom the uterus has closed immediately after the purification, conceive even while menstruating, but do not conceive afterwards. The catamenia sometimes occur even in pregnant women. Such women usually bear imperfect children, and their offspring either do not grow up, or are weakly. 3. It frequently happens that from the want of sexual intercourse, or from youth and the period of life, or from long abstinence, the uterus descends, and the catamenia occur several times in the month, until they conceive; after which the parts return to their proper place: and sometimes even in women with a good habit of body, if the humours are abundant, an effusion of the semen takes place if it is too moist.