Yoreh Deah Siman 24 Seif 15

 

טו עִקּוּר כֵּיצַד, כְּגוֹן שֶׁנֶּעֱקַר הַקָּנֶה אוֹ הַוֵּשֶׁט מֵהַלֶּחִי וּמֵהַבָּשָׂר, וְנִשְׁמַט אֶחָד מֵהֶם אוֹ שְׁנֵיהֶם קֹדֶם גְּמַר שְׁחִיטָה; אֲבָל אִם שָׁחַט אֶחָד בְּעוֹף אוֹ רֻבּוֹ, וְאַחַר כָּךְ נִשְׁמַט הַשֵּׁנִי, שְׁחִיטָתוֹ כְּשֵׁרָה; נִשְׁמַט אֶחָד מֵהֶם וְאַחַר כָּךְ שָׁחַט אֶת הַשֵּׁנִי, שְׁחִיטָתוֹ פְּסוּלָה.

 

Seif 15

 

What is meant by “uprooting”? When the windpipe or the gullet is ripped from the jaw and from the flesh and one or both of them slips before slaughter has been completed. If one [sign] in a fowl is slaughtered or most and afterward the second slipped, his slaughter is kosher. If one [sign] slips and afterward he slaughters the second his slaughter is not acceptable.