יורה דעה ק׳Yoreh De'ah 100

Se’if 1א׳

בְּרִיָּה, דְּהַיְנוּ כְּגוֹן נְמָלָה אוֹ עוֹף טָמֵא, וְגִיד הַנָּשֶׁה, וְאֵבֶר מִן הַחַי, וּבֵיצָה שֶׁיֵּשׁ בָּהּ אֶפְרוֹחַ וְכַיּוֹצֵא בָהֶם, אֲפִלּוּ בְּאֶלֶף לֹא בָּטֵל. וְאֵין לוֹ דִּין בְּרִיָּה, אֶלָּא אִם כֵּן הוּא דָּבָר שֶׁהָיָה בּוֹ חַיּוּת, לַאֲפוּקֵי חִטָּה אַחַת שֶׁל אִסוּר. וְכֵן צָרִיךְ שֶׁיְּהֵא דָּבָר שֶׁאָסוּר מִתְּחִלַּת בְּרִיָּתוֹ, לַאֲפוּקֵי עוֹף טָהוֹר שֶׁנִּתְנַבֵּל וְשׁוֹר הַנִּסְקָל. וְכֵן צָרִיךְ שֶׁיִּהְיֶה דָּבָר שָׁלֵם, שֶׁאִם יֵחָלֵק אֵין שְׁמוֹ עָלָיו, לַאֲפוּקֵי חֵלֶב. וְכֵן צָרִיךְ. שֶׁיִּהְיֶה שָׁלֵם. הַגָּה: וְעִקַּר גִּיד הַנָּשֶׁה אֵינוֹ אֶלָּא עַל הַכַּף בִּלְבַד, וְהוּא כְּרֹחַב ד' אֶצְבָּעוֹת, וְאִם הוּא שָׁלֵם מִקְרֵי בְּרִיָּה. (בְּאָרֹךְ כְּלָל כ"ח).

A creature (that is, something like an ant or an unkosher bird, or a sciatic nerve, or a limb of a living animal, or an egg with a chick inside, and such things) is never nullified even in 1000 times. Something will not be considered a "creature" in this context unless it is something which has had life, thus a single grain of forbidden wheat would not count. It must also be something which was forbidden at its creation (thus excluding a kosher bird which died a a natural death [and is thus unkosher only because it had no shechita], and an ox which was put to death under a court ruling). Also it must be a whole thing, such that it would be called something different were it to be split apart (thus excluding forbidden animal fats). And it must also be whole. NOTE: The main forbidden sciatic nerve is only on the /kaf/ , and it is about 4 fingerbreadths wide, and if it is whole it *is* called a "creature".If the [beriah] fell into a pot of soup and was lost, it is all forbidden.

Se’if 2ב׳

דָּבָר שֶׁהוּא בְּרִיָּה שֶׁנִּתְבַּשֵּׁל עִם הַהֶתֵּר, אִם אֵינוֹ מַכִּירוֹ הַכֹּל אָסוּר, וְהָרֹטֶב בְּנוֹתֵן טַעַם. וְאִם מַכִּירוֹ, זוֹרְקוֹ. וְהָאֲחֵרִים וְהָרֹטֶב צָרִיךְ שֶׁיִּהְיֶה בָּהֶם ס' כְּנֶגְדּוֹ, חוּץ מִגִּיד הַנָּשֶׁה שֶׁאֵין טַעֲמוֹ אוֹסֵר, דְּאֵין בַּגִּידִים בְּנוֹתֵן טַעַם. אֲבָל שַׁמְנוֹ, אוֹסֵר, וְצָרִיךְ שִׁשִּׁים כְּנֶגְדּוֹ לְהַתִּיר הָרֹטֶב. לְפִיכָךְ יָרֵךְ שֶׁנִּתְבַּשֵּׁל עִם גִּידוֹ, אִם מַכִּירוֹ זוֹרְקוֹ, וְכָל הַשְּׁאָר מֻתָּר, אִם יֵשׁ בּוֹ ס' כְּנֶגֶד שַׁמְנוֹ. וְאִם אֵינוֹ מַכִּירוֹ, כָּל הַחֲתִיכוֹת אֲסוּרוֹת. וְאִם יֵשׁ בַּקְּדֵרָה ס' כְּנֶגֶד הַשֻּׁמָּן, מֻתָּר הָרֹטֶב; וְאִם לָאו, אָסוּר. וְאִם נִמּוֹחַ הַגִּיד וְאֵינוֹ נִכָּר, צָרִיךְ גַּם כֵּן ס' כְּנֶגְדּוֹ.

Something which is a [beriah] which was cooked with [heter], if it is not recognizable: all of the solids are forbidden and the liquid would be subject to the laws of [noten taam]. If it is recognizable: throw out the piece and the rest of the solid and liquid combined require 60 times the amount.(except the gid hanashe which does not give off a taste strong enough to forbid. however its' oils do forbid and would require 60 times to permit the liquid). Therefore the [yerech] which was cooked with its nerve if it is recognizable: throw the piece away and the the rest is permitted if there is 60 times the amount the oils. If it is not recognizable: all of the pieces are forbidden. If there is in the pot 60 times the oils the liquid is permitted and if not it is forbidden. If the nerve was dissolved [nimuach] and is not recognizable you would require 60 times the nerve to permit it.

Se’if 3ג׳

קְדֵרָה שֶׁל מָרָק שֶׁנָּפַל שָׁם בְּרִיָּה וְנֶאֶבְדָה, אָסוּר הַכֹּל.

Regarding a pot of soup that had a [beriah] fall into it and was lost in the mixture, everything becomes forbidden. ...