Since land is free and no one will voluntarily work for another, such additional workers as are needed must be obtained and bound to the master by coercion. In this zone two very remarkable consequences follow from the fact that very few slaves are needed for workers. The first is the practice of cannibalism, once universal in this zone, and still in vogue throughout vast regions. The bountiful food supply attracts immigrants from all sides, and the result is a condition of chronic warfare. When one tribe defeats another the question arises, What is to be done with the prisoners? As they cannot be profitably employed as industrial workers, they are used to supplement a too exclusive vegetable diet. Wars come to be waged expressly for the sake of obtaining human flesh for food. The Monbuttu eat a part of their captives fallen in battle, and butcher and carry home the rest for future consumption. They bring home prisoners not to reduce to slavery but as butcher-meat to garnish future festivals. A second consequence of the limited demand for slaves is that war captives are sold to foreigners. Adjacent to the banana zone are zones of agriculture, where slaves are in great request, and, during the European connection with the slave trade, the normal demand for slaves in this zone was greatly heightened. Among the Niam Niam all prisoners belong to the monarch. He sells the women and keeps the children for slaves. Hence, the banana zone has been the great reservoir for supplying slaves to other parts of the world. Hundreds of thousands of slaves came from this zone to the West Indies, and to the slave states of North and South America. In Dahomey and Ashanti war captives used to be sold "en bloc" to white traders at so much per capita. In the agricultural zones to the north and south nature is more niggardly, though she yields enough, when coaxed by the hoe, to permit of a large class of parasites. The labor of maintenance is more onerous than in the banana zone. While the heat and humidity are not so great the work is more grievous because of its greater quantity and monotony. The motive to shift the work is, therefore, very strong and the demand for slaves is very great. In fact, the ratio of slaves to freemen is about three or four to one. As land is free and the resources open, the only means of obtaining workers is by coercion. The supply of slaves is kept up by kidnapping, by warfare upon weak tribes, by the purchase of children from improvident parents, and by forfeiture of freedom through crime.