Sentence:  ... the ore-smelting furnace is like a pregnant woman. ... For example, the furnace is described as the reproductive organs of a woman in one of the lessons in the Venda "domba" ritual while the <WSD>tewel</WSD> pipes are described as being symbolically male (Blacking 1969, p. 167). 
Meaning of the word marked with <WSD> tags:  A vent or chimney or pipe, especially one leading into a furnace or bellows.