And if it enters your mind that the mitzva is specifically to move the simanim behind the nape and pinch them, why did the tanna say specifically that if one pinches in this manner it is valid? Even if one slaughters from the nape in this manner the slaughter would be valid. Rather, must one not conclude from it that the proper understanding is: One may even move the simanim behind the nape and pinch, and the mishna is referring to a case where one did not move the simanim behind the nape.

Rabbi Yannai says: The young ones [rovin], the sons of Rabbi Ḥiyya, shall receive their response that rejects their statement from that which is taught in the mishna: It is found that that which is valid for slaughter is not valid for pinching and that which is valid for pinching is not valid for slaughter. What does this statement serve to exclude? Does it not serve to exclude the case where one moves the simanim behind the nape, teaching that it is valid only for slaughter and not for pinching?

Rabba bar bar Ḥana said: No, perhaps it serves to exclude one who uses a tooth or a fingernail that is not detached, which are valid for pinching and not valid for slaughter. The Gemara objects: That could not be, as the tanna teaches explicitly the case of a tooth and a fingernail in a mishna (15b), and there was no need to repeat it.

Rather, Rabbi Yirmeya said: The statement of the mishna: That which is valid for slaughter is not valid for pinching, serves to exclude drawing back and forth. One who pinches may not cut the simanim by drawing his fingernail back and forth. Rather, he must press and cut them in one motion. The Gemara asks: This works out well according to the one who says: Drawing back and forth for pinching is not valid, but according to the one who says: It is valid, what is there to say? The Gemara answers: The sons of Rabbi Ḥiyya hold in accordance with the one who says: Drawing back and forth for pinching is not valid.

Rav Kahana says: The mitzva of pinching is that one cuts with his fingernail from the nape and continues downward, and that is its mitzva. Rabbi Avin thought to say: Cuts and continues downward, yes; draws back and forth, no. Rabbi Yirmeya said to him: All the more so that drawing back and forth for pinching is valid. The Gemara asks: And what is the meaning of the phrase: That is its mitzva, which indicates that it is specifically in that manner? The Gemara answers: Say that it means: That too is its mitzva.

§ Rabbi Yirmeya says that Shmuel says: Any place that is valid for slaughter on the throat is correspondingly valid for pinching on the nape. By inference, any place on the throat that is not valid for slaughter is not valid for pinching. The Gemara asks: What does this statement serve to exclude? If we say that it serves to exclude ripping the simanim from their place before cutting them, which is invalid with regard to pinching just as with regard to slaughter, but didn’t Rami bar Yeḥezkel teach: There is no disqualification of ripping the simanim in the case of a bird?

Rav Pappa said: It serves to exclude pinching the occipital bone at the back of its head; just as it is not the place of slaughter, it is not the place of pinching. The Gemara asks: Isn’t it obvious that pinching at the back of its head is not valid? The Merciful One states: “Adjacent to its nape,” and not at its head.

The Gemara answers: What is its head that is not the place for pinching? It is the incline of its head, e.g., in a case where one began at the incline of its head and diverted and continued until he reached below to the place of the simanim, where he completed the pinching. Since he began the process in the incorrect location, it is invalid, similar to slaughter. And this is in accordance with the opinion that Rav Huna says that Rav Asi says, as Rav Huna says that Rav Asi says: If one diverted the knife upward and cut one-third of the windpipe and then cut two-thirds within the ring, the slaughter is not valid.

Rav Aḥa, son of Rava, said to Rav Ashi: With regard to that which Rami bar Yeḥezkel teaches: There is no disqualification for ripping simanim in a bird, we say it only according to the one who says: There is no source for the slaughter of a bird in the Torah.