1. טביעות עין is better than a סימן

On the previous Daf, the Gemara relates several stories where the kashrus of a found item (meat, or תכלת) was determined based on its being recognized. Rava commented that he used to think סימנא עדיף מטביעות עינא – an identifying mark is better than visual recognition, because a lost item is returned to someone who provides a סימן of the item, but not to someone who merely claims he recognizes it as his (unless he is a תלמיד חכם). But after hearing these rulings, he realized that טביעות עין is better than a סימן.

The Gemara proves the reliability of טביעות עין: otherwise, היאך סומא מותר באשתו – how is a blind man permitted to have relations with his wife, and how is anyone permitted to his wife at night, whom he cannot see? Rather, they must rely on טביעות עינא דקלא – recognition of her voice. Another proof: testimony from two witnesses that a person with certain סימנים killed someone is insufficient to execute him, but if they recognize a murderer with טביעות עין, we do execute him. [Still, a lost item is not returned based on טביעות עין, because of suspected dishonesty in monetary questions.]

1. Eating an entire גיד הנשה smaller than a כזית (בריה)

The next Mishnah states that one who eats a כזית of גיד הנשה receives malkus. אכלו ואין בו כזית חייב – If he ate [the entire גיד] and it did not contain a כזית, he is still liable to malkus. This is a machlokes Tannaim in a Baraisa: the Tanna Kamma says one is liable for eating an entire גיד הנשה which is smaller than a כזית, but Rebbe Yehudah says he is not liable unless it contains a כזית. The Rabbonon hold בריה היא – it is an entire creation, and incurs punishment with less than the standard shiur. Rebbe Yehudah holds that because אכילה כתיבא ביה – the term “eating” is written regarding [the גיד הנשה prohibition], it requires a כזית (the shiur for halachic “eating”) to be liable. The Rabbonon hold that the term "אכילה" obligates multiple sets of malkus for eating a גיד הנשה containing multiple כזיתים.

1. גיד הנשה cooked in the ירך prohibits בנותן טעם, but roasting does not spread flavor

The next Mishnah states that if a thigh was cooked with the גיד הנשה still in it, אם יש בה בנותן טעם – if [the thigh] contains an amount of meat so that the גיד הנשה gives flavor to it, the thigh is forbidden. This is measured כבשר בלפת – like meat in turnips, i.e., if meat the size of the גיד would give a discernible flavor when cooked in turnips the size of the thigh, the thigh is prohibited. The Mishnah proceeds to teach other cases where a גיד הנשה, or נבילה, prohibits food by imparting flavor through cooking.

Shmuel limits this ruling (that the גיד’s prohibited flavor is spread throughout the thigh) to where it was cooked together, אבל נצלה בה – but if [the גיד] was roasted with [the thigh], קולף ואוכל עד שמגיע לגיד – one may peel and eat until he reaches the גיד, i.e., he may eat all the meat surrounding the גיד הנשה, because roasting does not spread its flavor. [Tosafos adds, however, that the meat immediately adjacent to the גיד does absorb flavor and must be removed.] Meat roasted with cheilev is completely forbidden, דמפעפע – because [the cheilev flavor] spreads throughout the meat.