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מסכת חולין פרק ז משנה ה

Note:  While the term "גיד" is commonly translated as "sinew", as used in the mishnah it includes tendons, ligaments, nerves, blood vessels and other cord-like tissue.  For the purpose of simplicity, when used generically below it is translated as "sinew."

גיד הנשה A sciatic nerve
שנתבשל עם הגידים that was cooked with [other permitted] sinews
בזמן שמכירו [even] when he can discern it [and remove the forbidden sciatic nerve from the other sinews]
בנותן טעם [the mixture is nonetheless prohibited] when it [the sciatic nerve] imparts flavor,
ואם לאו כלן אסורין and if not (if he cannot pick out the forbidden substance) it is all prohibited.  (Even at a ratio of 1:60 this will apply, as a sciatic nerve is considered a 'beriah' [בריה], an entire formation, which cannot be nullified).
והרטב בנותן טעם

and [if this mixture of permitted and prohibited sinews, from which the forbidden sciatic nerve is not discernable, were] in a broth, [then only] when it [the sciatic nerve] imparts flavor [will the broth be prohibited].  (The other sinews remain prohibited even if it did not impart flavor, however in that case we would permit the broth when the forbidden substance is 1/60 or less than the rest of the items in the pot.)

וכן חתיכה של נבילה And similarly a piece of a neveilah,
וכן חתיכה של דג טמא and similarly a piece of a non-kosher fish,
שנתבשלו עם החתיכות that were cooked with other pieces,
בזמן שמכירן [even] when they are discernable [and are removed]
בנותן טעם [the mixture is nonetheless prohibited] when it [the sciatic nerve] imparts flavor,
ואם לאו כלן אסורות

and if not (if he cannot pick out the forbidden substance) it is all prohibited.  (As the forbidden pieces are considered worthy of being served to a guest, they cannot be nullified even at a ration of 1:60),

והרטב בנותן טעם and [if such a  mixture of permitted and prohibited substances were] in a broth, [then only] when it [the forbidden substance] imparts flavor [will the broth be prohibited].
 

פרק ז משנה ו

נוהג בטהורה [The prohibition against eating the sciatic nerve] is observed by kosher [animals]
ואינו נוהג בטמאה and is not observed by non-kosher animals (such that if one were to eat it from a non-kosher animal, one would only have committed one transgression);
רבי יהודה אומר Rabbi Yehuda says
אף בטמאה also by non-kosher animals.
אמר רבי יהודה Rabbi Yehuda said,
והלא מבני יעקב "Was it not from [the time of] the children of Yaakov
נאסר גיד הנשה that the sciatic nerve was prohibited [as set forth in Bereishis 32:33],
ועדין בהמה טמאה and non-kosher animals were as yet
מותרת להם permitted to them [until the Torah was given at Sinai]?"
אמרו לו They said to him:
בסיני נאמר "At Sinai [the prohibition] was stated [for the first time],
אלא שנכתב במקומו

only it was written in its place [in the chronology of the Torah]."