Menstruation has always been of interest, not only to the student of medicine, but to the lay-observer as well. In olden times there were many opinions concerning its causation, all of which, until the era of physiologic investigation, were of superstitious derivation. Believing menstruation to be the natural means of exit of the feminine bodily impurities, the ancients always thought a menstruating woman was to be shunned; her very presence was deleterious to the whole animal economy, as, for instance, among the older writers we find that Pliny remarks: "On the approach of a woman in this state, must will become sour, seeds which are touched by her become sterile, grass withers away, garden plants are parched up, and the fruit will fall from the tree beneath which she sits." He also says that the menstruating women in Cappadocia were perambulated about the fields to preserve the vegetation from worms and caterpillars. According to Flemming, menstrual blood was believed to be so powerful that the mere touch of a menstruating woman would render vines and all kinds of fruit-trees sterile. Among the indigenous Australians, menstrual superstition was so intense that one of the native blacks, who discovered his wife lying on his blanket during her menstrual period, killed her, and died of terror himself in a fortnight. Hence, Australian women during this season are forbidden to touch anything that men use. Aristotle said that the very look of a menstruating woman would take the polish out of a mirror, and the next person looking in it would be bewitched. Frommann mentions a man who said he saw a tree in Goa which withered because a catamenial napkin was hung on it. Bourke remarks that the dread felt by the American Indians in this respect corresponds with the particulars recited by Pliny. Squaws at the time of menstrual purgation are obliged to seclude themselves, and in most instances to occupy isolated lodges, and in all tribes are forbidden to prepare food for anyone save themselves. It was believed that, were a menstruating woman to step astride a rifle, a bow, or a lance, the weapon would have no utility. Medicine men are in the habit of making a "protective" clause whenever they concoct a "medicine," which is to the effect that the "medicine" will be effective provided that no woman in this condition is allowed to approach the tent of the official in charge.