The Mishna (96b) teaches that if the gid ha-nasheh had not been removed, and an animal’s thigh was cooked together with the sciatic nerve such that there was so much of the nerve as to impart a flavor to the meat of the thigh, it is forbidden. The Mishna continues by asking “How does one measure this?” and explains that we view it as though the meat had been cooked with turnips.
On today’s daf, Rav Huna explains the meaning of the Mishna. If, when meat and turnips are cooked together in the same proportions as is found in the sciatic nerve and the thigh respectively, the meat imparts its flavor to the turnips, then the thigh would be forbidden on account of the taste of the forbidden nerve. As we have learned (above, daf 97), the Sages estimate that meat cannot impart its taste to any substance that is cooked with it if the latter is sixty times as large in bulk as the meat.
The difficulty in estimating whether the taste of the gid ha-nasheh affects the taste of the meat stems from the fact that different elements all have a similar, meaty taste. Even if the difference in taste could be ascertained, a Jew could not taste-test it, since there is a possibility that the forbidden taste was absorbed by the meat and is forbidden. Giving it to an expert non-Jewish cook to taste is not raised as a possibility. The Ḥatam Sofer suggests that this is because the non-Jew can be trusted to testify only about foods with which he is familiar. In this case, since no non-Jew ever eats the animal’s thigh with the sciatic nerve removed, he will be unable to tell us whether or not the taste of the nerve has changed the taste of the meat.
This discussion notwithstanding, the Gemara points out that Rabbi Yishmael, the son of Rabbi Yoḥanan ben Beroka disagrees with the Mishna and rules that the gid ha-nasheh has no taste whatsoever and cannot impart its taste into the meat that surrounds it. This opinion is ultimately accepted by the Gemara and is the accepted halakha.