Purity, pollution and the invisible snake in southern Africa.

There exists in parts of southern and eastern Africa an apparently widespread belief in the existence of an invisible, internal "snake," often described as a power or force of some kind that dwells in the stomach but that can move throughout the upper body. Although some anthropologists have described this snake as related to witchcraft, findings from diverse parts of Mozambique, South Africa and elsewhere suggest that it may (also) be thought of as a symbolic expression of the need to respect the human body, specifically to protect it against the introduction of impurity. Belief in nyoka, as Tsonga- and Shona-speakers call the invisible snake, suggests the importance of purity and pollution beliefs as they relate to health in a particular society; the presence of nyoka belief may even be taken as an empirical measure of their importance. Going beyond nyoka, it is argued that pollution beliefs are more central in southern African ethnomedicine than the literature suggests, perhaps more so than witchcraft and sorcery beliefs. It is hypothesized that pollution-related illnesses tend to be roughly coterminous with diseases biomedically classified as contagious. Apart from ethnographic and theoretical significance, establishing the nature and centrality of pollution beliefs, aided by analysis of cultural metaphors such as the invisible snake, can point to culturally appropriate ways of presenting health education messages in societies where pollution beliefs are important. Pollution beliefs may be characterized as quasi-naturalistic and they in fact represent an area of potential interface between indigenous and cosmopolitan medicine-far more than witchcraft beliefs.