These worms are usually present in great numbers, there being as a rule from 500 to 2,000 of them, and as they unquestionably live at least eight or ten years, the unfortunate victim suffers for a long period of time as a result of their presence. While living in the intestines the females lay enormous numbers of eggs which pass out with the feces, and under suitable conditions of temperature and moisture there develops within each of them, within from two to three days, a minute snake-like embryo which bursts through the shell of the egg and passes into the neighboring earth. Here the embryos live for considerable periods of time, and, ultimately, may infect other individuals, or those from whom the eggs were passed. There are at least two ways by which these embryos gain entrance into the human body. Some do so by getting into drinking-water and being swallowed; but, extraordinarily, they most frequently penetrate through the skin. When this happens the parasite, in passing through the skin, produces the disease known as "ground-itch." The vast majority of the victims of this affection are children with whose skin the embryo comes in contact while they go barefooted during the summer months. _Course of the Disease._--Having entered through the skin, the embryos of the hook-worm, moving by a circuitous route finally reach the intestines, and, grasping hold of the mucous membrane with their saw-like teeth, they begin to suck blood and grow until they reach the size of the adult worm in about a month or six weeks. Depending upon the number which have gained entrance, and the susceptibility of the individual, there now begins to develop symptoms of profound anaemia; the skin of the child becomes very pale, and assumes a sort of yellowish hue, and in cases where there is a severe infection, the victim begins to suffer with shortness of breath and dropsy. When this occurs the patient sometimes dies, but more commonly death results from contracting some other disease, which, under ordinary conditions, would produce no serious results. One of the most unfortunate effects of this malady is that when children become infected they cease to grow, and frequently retain the appearance of early youth even after they have reached full maturity in years. These unfortunates are generally incorrectly regarded as dirt-eaters. The symptoms frequently last over a period of many years, as in the intestines of these victims the worms that originally infect them live certainly eight or ten years, and during this period it is beyond question true that additions to the original number are frequently received.