Gustav Nachtigal,l the famous nineteenth-century traveller and explorer of the Sahara and Sudan, relates that the women of Wadai, a region in the Sudan, rarely go out without their toothbrushes in the corner of their mouths. These toothbrushes are, as he says, prepared from the wood of the siwak (Salvadora persica L.), which has been made fibrous at the end, and as soon as they sit down they us...