Niddah

R. Giddal citing Rab ruled: If a woman gave to her child some cooked food and then performed her ritual immersion and ascended from the water,  her immersion has no validity,  because, though there may be no food  now,  it may well be assumed that it had fallen off with the drippings. Rami b. Abba  ruled: Scars  constitute no interposition  during the first  three days;  henceforth they constitute an interposition. Mar Ukba ruled: Pus within the eye constitutes no interposition when it is moist, but when it is dry it constitutes one. When is it called 'dry'? — From the time it begins to turn yellow. Samuel ruled: Stibium within the eye constitutes no interposition but on the outside of the eye it constitutes one. If a woman's eyes were twitching it constitutes no interposition even if it is on the outside of the eye. R. Johanan ruled: If a woman  opened her eyes too wide  or shut them too closely,  her immersion has no validity. Resh Lakish ruled: A woman must perform immersion only when standing in her natural position;  as we have learnt:  A man  is inspected  in the same position as when he hoes  or  gathers olives;  and a woman  is inspected  in the same position as when she weaves  or  suckles her child. Rabbah b. R. Huna  stated, 'One knotted hair constitutes an interposition,