Niddah

R. Joshua b. Levi cursed the man who sleeps on his back.  But this, surely, is not correct,  for did not R. Joseph rule that one lying on his back should not read the shema',  from which it follows, does it not, that it is only the shema' that he must' not read but that he may well sleep in this manner? — As regards sleeping on one's back this is quite proper if one slightly inclines sideways, but as regards the reading of the shema' even if one inclines sideways this is forbidden.  But did not R. Johanan turn slightly on his side and read the shema'? — R. Johanan was different [from other people] because he was corpulent. MISHNAH. IT IS THE CUSTOM OF THE DAUGHTERS OF ISRAEL WHEN HAVING MARITAL INTERCOURSE TO USE TWO TESTING-RAGS, ONE FOR THE MAN AND THE OTHER FOR HERSELF,  AND VIRTUOUS WOMEN PREPARE ALSO A THIRD RAG WHEREBY TO MAKE THEMSELVES FIT FOR MARITAL DUTY.  IF A VESTIGE OF BLOOD IS FOUND ON HIS RAG  THEY ARE BOTH UNCLEAN  AND ARE ALSO UNDER THE OBLIGATION OF BRINGING A SACRIFICE.  IF ANY BLOOD IS FOUND ON HER RAG IMMEDIATELY AFTER THEIR INTERCOURSE THEY ARE BOTH UNCLEAN AND ARE ALSO UNDER THE OBLIGATION OF BRINGING A SACRIFICE. IF, HOWEVER, ANY BLOOD IS FOUND ON HER RAG AFTER A TIME THEY ARE UNCLEAN  BY REASON OF DOUBT  BUT EXEMPT FROM THE SACRIFICE. WHAT IS MEANT BY 'AFTER A TIME'? WITHIN AN INTERVAL IN WHICH SHE CAN DESCEND FROM THE BED AND WASH HER FACE.  BUT [IF BLOOD WAS FOUND SOME TIME] AFTER SUCH AN INTERVAL SHE CAUSES UNCLEANNESS RETROSPECTIVELY  FOR A PERIOD OF TWENTY-FOUR HOURS  BUT SHE DOES NOT CAUSE THE MAN WHO HAD INTERCOURSE WITH HER TO BE UNCLEAN.  R. AKIBA RULED: SHE  ALSO CAUSES THE MAN WHO HAD INTERCOURSE WITH HER TO BE UNCLEAN.  THE SAGES, HOWEVER, AGREE WITH R. AKIBA THAT ONE WHO OBSERVED A BLOODSTAIN CONVEYS UNCLEANNESS TO THE MAN WHO HAD INTERCOURSE WITH HER. GEMARA. But  why should not the possibility be considered that the blood might be that of a louse?  — R. Zera replied that place is presumed to be tested as far as a louse is concerned. There are others, however, who reply: It is too narrow for a louse. What is the practical difference between them?  — The practical difference between them is the case where a crushed louse was found.  According to the reply  that the place is presumed to be tested, this must have come from somewhere else,  but according to the reply  that the place is too narrow it might be presumed that the attendant  has crushed it. It was stated: If a woman examined herself with a rag that she had previously examined,  and then she pressed it against her thigh on which she found blood on the following day, Rab ruled: She  is subject to the uncleanness of a menstruant.  Said R. Shimi b. Hiyya to him: But, surely, you told us, 'She has only to take the possibility  into consideration'. It was also stated: Samuel ruled: She is subject to the uncleanness of a menstruant.  And so they also ruled at the schoolhouse: She is subject to the uncleanness of a menstruant. It was stated: If a woman examined herself with a rag which she had not previously examined and having put it into a box she found upon it, on the following day, some blood,  R. Joseph stated: Throughout all his lifetime R. Hiyya regarded [her] as unclean but in his old age he ruled that [she] was clean. The question was raised: What  does he  mean: That throughout all his  lifetime he regarded [her] as menstrually unclean  and in his old age he ruled that [she] was clean as far as menstruation is concerned but unclean on account of the bloodstain,  or it is possible that throughout his lifetime he regarded [her] as unclean on account of the stain  and in his old age he ruled that [she] was absolutely  clean? — Come and hear what was taught: If a woman examined herself with a rag which she had not previously examined and having put it into a box she found upon it, on the following day, some blood, Rabbi ruled: She is regarded as menstrually unclean,  and R. Hiyya ruled: She is regarded as unclean on account of the bloodstain.