The demand quickly grew as tobacco, referred to as "brown gold", revived the Virginia joint stock company from its failed gold expeditions. In order to meet demands from the Old World, tobacco was grown in succession, quickly depleting the soil. This became a motivator to settle west into the unknown continent, and likewise an expansion of tobacco production. Indentured servitude became the primary labor force up until Bacons Rebellion, from which the focus turned to slavery. This trend abated following the American Revolution as slavery became regarded as unprofitable. However, the practice was revived in 1794 with the invention of the cotton gin.Frenchman Jean Nicot (from whose name the word nicotine is derived) introduced tobacco to France in 1560, and tobacco then spread to England. The first report of a smoking Englishman is of a sailor in Bristol in 1556, seen "emitting smoke from his nostrils". Like tea, coffee and opium, tobacco was just one of many intoxicants that was originally used as a form of medicine. Tobacco was introduced around 1600 by French merchants in what today is modern-day Gambia and Senegal. At the same time, caravans from Morocco brought tobacco to the areas around Timbuktu, and the Portuguese brought the commodity (and the plant) to southern Africa, establishing the popularity of tobacco throughout all of Africa by the 1650s. Soon after its introduction to the Old World, tobacco came under frequent criticism from state and religious leaders.
Despite the limited, 13-week lifespan of individual pinworms, autoinfection (infection from the original host to itself), either through the anus-to-mouth route or through retroinfection, causes the pinworms to inhabit the same host indefinitely. Life cycle
The life cycle begins with eggs being ingested. The eggs hatch in the duodenum (first part of the small intestine). The emerging pinworm larvae grow rapidly to a size of 140 to 150 micrometres, and migrate through the small intestine towards the colon. During this migration they moult twice and become adults. Females survive for 5 to 13 weeks, and males about 7 weeks. The male and female pinworms mate in the ileum (last part of the small intestine), whereafter the male pinworms usually die, and are passed out with stool. The gravid female pinworms settle in the ileum, caecum (beginning of the large intestine), appendix and ascending colon, where they attach themselves to the mucosa and ingest colonic contents. Almost the entire body of a gravid female becomes filled with eggs. The estimations of the number of eggs in a gravid female pinworm ranges from about 11,000 to 16,000. The egg-laying process begins approximately five weeks after initial ingestion of pinworm eggs by the human host. The gravid female pinworms migrate through the colon towards the rectum at a rate of 12 to 14 centimetres per hour.