Gender categories may be defined by criteria other than -- or in addition to -- genital appearance and behavior. In discussing Hua notions of pollution and male pregnancy, Meigs notes that in addition to the criteria named above, gender classification may also be based on fluids that are associated with sexuality. These include menstrual blood, vaginal secretions, parturitional fluids, and sperm. Meigs (1976:405) says:
As these fluids are transferable between the two genitally different classes, this classification permits cross overs: where a genitally male person is classified as female through his contamination by female fluids, and a genitally female person as male by means of transfer of pollution out of her body.
As a result of their transfer of sexual effluvia and the cross over of classification, both men and women experience gender change. Old women become socially equivalent to males, for they may live in the men's house, they are privy to male secret knowledge, and they must observe rules that are normally limited to young men. Old men, on the other hand, take on some aspects of female social status. For example, at weddings they eat with women and children in a space that is segregated from the other men. They are placed in the category of polluting people that includes children, fertile women, and post-menopausal women with less than three children (Meigs 1976:402). Meigs clearly demonstrates that, for the Hua, gender is experienced and transmitted along with the sexual fluids that define it.