Niddah

R. Aha son of Raba taught this  in the name of R. Eleazar in the direction of leniency. From any gezerah shawah none of whose terms is available for deduction, one may make the deduction and one may also offer a refutation; if one of its terms only is available for the purpose, deduction, according to R. Ishmael, may be made and no refutation may be offered, while according to the Rabbis deduction may be made and a refutation may be offered; and if two of its terms are available for deduction, all agree that deduction may be made and no refutation may be offered. But according to the Rabbis  what is the practical difference between one whose one term is available for deduction and one none of whose terms is available for deduction? — The practical difference between them is the case where you find a gezerah shawah one of whose terms is available for deduction and another none of whose terms is available for the purpose, and neither the one nor the other can be refuted, in such a case we must leave the one neither of whose terms is available and make deduction from the one of which one term is available. But what refutation is there in this case?  — One might object:  A man is different  since he contracts uncleanness  even when he is alive. R. Hiyya b. Abba citing R. Johanan also stated,  This is the reason of R. Meir: Since the expression of 'forming' has been used in its case as in that of man. Said R. Ammi to him: Now then, If an abortion was in the shape of a mountain would the woman who aborted it  be unclean by reason of the birth because it is said, For, lo, He that formeth  the mountains and createth the wind?  — The other replied: Does she ever abort a mountain? She can only abort something in the shape of a stone, and that can only be described as a lump.  But then, if the abortion was some inflated object would the woman who aborted it  be unclean by reason of the birth because the expression of 'creating' has been used about it as about man, since it is written, And createth  the wind?  And should you reply: it  is not available for deduction,  [it could be retorted:] Since it could have been written, 'Formeth the mountains and the wind', and yet it was written 'And createth the wind' it may be inferred, may it not, that it  was intended to be made available for deduction? — The other replied: An analogy for legal purposes may be drawn between words that occur in the Pentateuch  but no analogy may be drawn between words that occur respectively in the Pentateuch and in the post-Pentateuchal books. Rabbah  b. Bar Hana citing R. Johanan stated, This is the reason of R. Meir: Because [the pupils  of] their  eyes are similar to those of human beings. Now then, if an abortion was in the likeness of a serpent would the woman who aborted it  be unclean on account of the birth since its eye-ball is round like that of a human eye? And should you suggest that the law is so indeed [it could be retorted]: Why then was not the serpent mentioned?  — If the serpent had been mentioned  it might have been presumed that only in the case of the serpent do the Rabbis disagree with R. Meir, since the expression of 'forming' was not written about it but that in the case of a beast or a wild animal they do not differ from him since the expression of 'forming' had been written about it.  But was it not stated in regard to blemishes,  'One whose eyeball is like that of a man'?  — This is no difficulty, the one  refers to the black of the eye  while the other refers to the slit. R. Jannai stated, This is the reason of R. Meir: Because their  eyes are fixed in the front of their heads  like those of men. But what about  a bird whose eyes are not fixed in the front of its head and R. Meir nevertheless ruled that it is a cause of uncleanness? — Abaye replied: This  applies only to the kadia  and the kipufa.  It  does not then apply to other birds! An objection was raised: R. Hanina b. Gamaliel  stated, I approve of the view of R. Meir in regard to beasts and wild animals and that of the Sages in regard to birds. Now what did he mean by 'birds'? If it be suggested: kadia  and kipufa  [the difficulty would arise]: Wherein do beasts and wild animals differ [from other creatures]? [Obviously in that] that their eyes are fixed in front of their heads like those of men. Now are not those of the kadia  and the kipufa  fixed in the same position?  Consequently  he must have meant other birds. Thus it may be implied, may it not, that R. Meir differs from the Rabbis in regard to the other birds?  — Some part is missing  and this is the correct reading: R. Hanina b. Gamaliel  stated, I approve of the view of R. Meir in regard to beasts and wild animals, this applying also to the kadia and the kipufa; and that of the Sages in regard to other birds; for even R. Meir disagreed with them only in regard to the kadia and the kipufa, but in the case of other birds he agrees with them. And so it was also taught: R. Eliezer son of R. Zadok stated: An abortion that had the shape of a beast or a wild animal is, according to the view of R. Meir, regarded as a valid birth, but according to the view of the Sages it is no valid birth; and in the case of birds an examination should take place. Now according to whose view should an examination take place? Obviously  according to that of R. Meir who ruled that the law  applied  to the kadia and the kipufa and not to the other birds! R. Aha son of R. Ika retorted: No; the examination should take place according to the Rabbis who ruled that kadia and kipufa are regarded as valid births  but not other birds. But wherein does the kadia or the kipufa in this respect differ from beasts and wild animals?  — In that they have jaws like those of men. R. Jeremiah enquired of R. Zera: According to R. Meir who ruled: 'A beast that was in a woman's body is a valid birth', what is the law where its father  received for it a token of betrothal?  — In what respect could this  ever matter? — In respect of causing its sister to be forbidden.  This then presumes  that it is viable! But did not Rab Judah citing Rab state: R. Meir gave his ruling  only because in the case of its own species  it is viable?  Said R. Aha b. Jacob: 'To such an extent did R. Jeremiah try  to make R. Zera laugh; but the latter did not laugh'. [Reverting to] the [previous] text, 'Rab Judah citing Rab stated: R. Meir gave his ruling only because in the case of its own species it is viable.' Said R. Jeremiah of Difti: