Halacha

הלכה א
חֲמִשָׁה דְּבָרִים מַפְסִידִין אֶת הַשְּׁחִיטָה. וְעִקַּר הִלְכוֹת שְׁחִיטָה לְהִזָּהֵר בְּכָל אַחַת מֵהֶן. וְאֵלּוּ הֵן. שְׁהִיָּה. דְּרָסָה. חֲלָדָה. הַגְרָמָה. וְעִקּוּר:
כסף משנה
1.
There are five factors that disqualify ritual slaughter and the fundamentals of the laws of shechitah are to guard against each of these factors: They are: shehiyah, dirasah, chaladah, hagramah, and ikur.1The Rambam describes each of these terms in the subsequent halachot in this chapter.

הלכה ב
שְׁהִיָּה כֵּיצַד. הֲרֵי שֶׁהִתְחִיל לִשְׁחֹט וְהִגְבִּיהַּ יָדוֹ קֹדֶם שֶׁיִּגְמֹר הַשְּׁחִיטָה וְשָׁהָה בֵּין בְּשׁוֹגֵג בֵּין בְּמֵזִיד בֵּין בְּאֹנֶס וְחָזַר הוּא אוֹ אַחֵר וְגָמַר אֶת הַשְּׁחִיטָה. אִם שָׁהָה כְּדֵי שֶׁיַּגְבִּיהַּ אֶת הַבְּהֵמָה וְיַרְבִּיצֶנָּה וְיִשְׁחֹט שְׁחִיטָתוֹ פְּסוּלָה. וְאִם שָׁהָה פָּחוֹת מִכְּדֵי זֶה שְׁחִיטָתוֹ כְּשֵׁרָה:
כסף משנה
2.
What is meant by shehiyah? A person began to slaughter and lifted up his hand before he completed the slaughter and waited. Whether he did so inadvertently, intentionally, or because of forces beyond his control, [the following rules apply] if he or another person completed the slaughter. If he waited the amount of time it would take to lift up the animal, cause it to lie down, and slaughter it, his slaughter is not acceptable. If he waited less than this amount of time, his slaughter is acceptable.

הלכה ג
הָיְתָה בְּהֵמָה דַּקָּה שִׁעוּר שְׁהִיָּתָהּ כְּדֵי שֶׁיַּגְבִּיהַּ בְּהֵמָה דַּקָּה וְיַרְבִּיצֶנָּה וְיִשְׁחֹט. וְאִם הָיְתָה גַּסָּה כְּדֵי שֶׁיַּגְבִּיהֶנָּה וְיַרְבִּיצֶנָּה וְיִשְׁחֹט. וּבְעוֹף כְּדֵי שֶׁיַּגְבִּיהַּ בְּהֵמָה דַּקָּה וְיַרְבִּיצֶנָּה וְיִשְׁחֹט:
כסף משנה
3.
With regard to a small domesticated animal:2I.e., a sheep or a goat., the measure of shehiyah is the amount of time it would take to lift up the animal, cause it to lie down, and slaughter it. With regard to a large domestic animal,3I.e., a cow. the measure of shehiyah is the amount of time it would take to lift up the animal, cause it to lie down, and slaughter it.4I.e., each animal is considered according to its category. It will take more time to deal with a large animal than a smaller one and the time factor is adjusted accordingly. With regard to a fowl, the measure of shehiyah is the amount of time it would take to lift up a small animal, cause it to lie down, and slaughter it.5The Rambam's ruling favors the opinion of Shmuel over Rav. In his Kessef Mishneh, Rav Yosef Caro explains that generally, we follow the principle that the halachah follows Rav's approach with regard to the Torah prohibitions. Nevertheless, in this instance, since there are other Sages who support Shmuel's view, the Rambam favors his opinion. In his Shulchan Aruch (Yoreh De'ah 23:2), in addition to the Rambam's view, Rav Yosef Caro quotes Rashi's position which rules much more stringently with regard to shehiyah for a fowl. The Rama states that the common custom is to disqualify any ritual slaughter involving shehiyah of the slightest time for both animals and fowl.

הלכה ד
שָׁחַט מְעַט וְשָׁהָה מְעַט וְחָזַר וְשָׁחַט מְעַט וְשָׁהָה מְעַט עַד שֶׁגָּמַר הַשְּׁחִיטָה וְלֹא שָׁהָה בְּפַעַם אַחַת שִׁעוּר הַשְּׁהִיָּה אֲבָל כְּשֶׁתַּחְשֹׁב כָּל זְמַן הַשְּׁהִיּוֹת יִצְטָרֵף מִכֻּלָּן שִׁעוּר שְׁהִיָּה הֲרֵי זוֹ סְפֵק נְבֵלָה. וְכֵן אִם שָׁהָה כְּדֵי שֶׁיַּגְבִּיהֶנָּה וְיַרְבִּיצֶנָּה וּכְדֵי שֶׁיִּשְׁחֹט כְּמוֹ מִעוּט הַסִּימָנִין בִּלְבַד לֹא כְּדֵי שֶׁיִּשְׁחֹט שְׁחִיטָה גְּמוּרָה הֲרֵי זוֹ סְפֵק נְבֵלָה:
כסף משנה
4.
When a person cut [the signs] for a while, waited for a while, cut for a while, waited for a while until he concluded the slaughter without waiting the measure that disqualifies an animal at any one time, but over the times he waited over the entire period would equal the measure of shehiyah, there is an unresolved doubt whether [the animal is considered] a nevelah.6Although the Ra'avad and Rav Moshe HaCohen dispute the Rambam's ruling, it is accepted by the Shulchan Aruch (Yoreh De'ah23:3). The Rama reiterates the stringency stated above.
Similarly, if he waited the amount of time it takes to lift up the animal, cause it to lie down, and cut only a portion of the signs, but not to slaughter it entirely, there is an unresolved doubt whether [the animal is considered] a nevelah.

הלכה ה
שָׁחַט רֹב אֶחָד בְּעוֹף אוֹ רֹב שְׁנַיִם בִּבְהֵמָה אַף עַל פִּי שֶׁשָּׁהָה חֲצִי הַיּוֹם וְחָזַר וְגָמַר חֲתִיכַת הַסִּימָנִין הֲרֵי זוֹ מֻתֶּרֶת. מֵאַחַר שֶׁנִּשְׁחַט בָּהּ כַּשִּׁעוּר הֲרֵי זֶה כִּמְחַתֵּךְ בְּשַׂר הַשְּׁחוּטָה:
כסף משנה
5.
If he slaughtered the majority of one of the signs for a fowl or the majority of both signs for an animal, the slaughter is permitted even if he waited half the day and then returned and finished cutting the signs.7In addition to the Rambam's view, the Shulchan Aruch (Yoreh De'ah 23:5) quotes the view of Rashi cited by the Tur that as long as the cutting of the signs is not completed, shehiyah can disqualify an animal. Hence, as an initial and preferred option, one should show respect for this view. The Rama rules even more stringently, stating that even after the fact, the slaughter is disqualified. For that reason, he continues, if the majority of the signs are cut, but the animal is lingering alive, rather than cut the signs further, one should hit it on its head to kill it. For since the minimum measure for slaughter was met, it is as if he is cutting slaughtered meat.

הלכה ו
שָׁחַט בַּקָּנֶה לְבַדּוֹ חֶצְיוֹ אוֹ מִעוּטוֹ וְשָׁהָה זְמַן מְרֻבֶּה הֲרֵי זֶה חוֹזֵר וְגוֹמֵר הַשְּׁחִיטָה וְאֵין בְּכָךְ כְּלוּם. אֲבָל אִם שָׁחַט רֹב הַקָּנֶה אוֹ שֶׁנִּקֵּב בַּוֵּשֶׁט כָּל שֶׁהוּא וְשָׁהָה כַּשִּׁעוּר בֵּין שֶׁחָזַר וְגָמַר הַשְּׁחִיטָה שֶׁהִתְחִיל בֵּין שֶׁשָּׁחַט שְׁחִיטָה גְּמוּרָה בְּמָקוֹם אַחֵר הֲרֵי זוֹ פְּסוּלָה. מִפְּנֵי שֶׁהַבְּהֵמָה אוֹ הָעוֹף שֶׁנִּפְסַק רֹב הַקָּנֶה שֶׁלָּהּ אוֹ שֶׁנִּקַּב הַוֵּשֶׁט בְּמַשֶּׁהוּ נְבֵלָה וְאֵין הַשְּׁחִיטָה מוֹעֶלֶת בָּהּ כְּמוֹ שֶׁיִּתְבָּאֵר:
כסף משנה
6.
If one cuts half or less of the windpipe and waits an extended period, he may return and complete the slaughter; [his previous acts] are of no consequence.8For until half of the windpipe is cut, the animal is not considered as trefe. If, however, he cut the majority of [an animal's] windpipe or perforated the gullet even slightly and then waited the [disqualifying] measure, [the slaughter] is unacceptable.9He cannot return and correct the slaughter, for the animal is already considered as a nevelah. [This applies] whether he returned and completed cutting where he began or slaughtered the animal entirely in a different place. [The rationale is] that when the majority of the windpipe is slit or the gullet of either an animal or a fowl is perforated even slightly, the animal is comparable to a nevelah and ritual slaughter is not effective for it, as will be explained.10Halachah 19.

הלכה ז
הִנֵּה נִתְבָּאֵר לְךָ שֶׁאֵין שְׁהִיָּה בַּקָּנֶה בָּעוֹף כְּלָל. שֶׁאִם שָׁחַט רֹב הַקָּנֶה וְשָׁהָה כְּבָר נִגְמְרָה שְׁחִיטָתוֹ כְּשֶׁחָזַר וְגָמַר מְחַתֵּךְ בָּשָׂר הוּא. וְאִם שָׁחַט בְּמִעוּט הַקָּנֶה וְשָׁהָה הֲרֵי זֶה חוֹזֵר וְשׁוֹחֵט כָּל זְמַן שֶׁיִּרְצֶה שֶׁאֵינָהּ נֶאֱסֶרֶת מִשּׁוּם נְבֵלָה עַד שֶׁיִּפָּסֵק רֹב הַקָּנֶה:
כסף משנה
7.
It is thus explained for you that the concept of shehiyah does not exist with regard to the windpipe of a fowl at all. For if he slit the majority of the windpipe and waited, he has already completed the slaughter of [the fowl]. When he goes back and completes it, it is as if he is cutting meat.11As stated in Halachah 5. If he slit less than half the windpipe and waited, he may return and [complete the] slaughter whenever he desires,12As stated in Halachah 6. for it is not disqualified as a nevelah unless the majority of the windpipe has been cut.

הלכה ח
שָׁחַט הָעוֹף וְשָׁהָה בּוֹ וְאֵינוֹ יוֹדֵעַ אִם נִקַּב הַוֵּשֶׁט אוֹ לֹא נִקַּב חוֹזֵר וְשׁוֹחֵט הַקָּנֶה לְבַדּוֹ בְּמָקוֹם אַחֵר וּמַנִּיחוֹ עַד שֶׁיָּמוּת וּבוֹדֵק הַוֵּשֶׁט מִבִּפְנִים. אִם לֹא נִמְצֵאת בּוֹ טִפַּת דָּם בְּיָדוּעַ שֶׁלֹּא נִקַּב וּכְשֵׁרָה:
כסף משנה
8.
[The following rules apply when] one slaughtered a fowl and waited, but does not know whether the gullet was perforated or not.13If the gullet was perforated, the slaughter is unacceptable. If not, it is acceptable. He should return and cut the windpipe alone in another place,14Theoretically, he could also cut the windpipe in the same place and complete the slaughter in that manner. Nevertheless, our Sages advised against doing so, for in this way, it is much easier to perforate the gullet when cutting the windpipe and thus he might disqualify the slaughter unnecessarily (Kessef Mishneh). See the Turei Zahav 23:6 who offers another rationale. As mentioned above, the Rama rules that whenever one waits during the slaughter of a fowl or an animal, the slaughter is disqualified.
A parallel law - slaughtering the animal in a different place - does not apply with regard to an animal. For to slaughter the animal, he must slit the gullet and we fear that he will cut at a place where it had been perforated previously (Kessef Mishneh).
let [the fowl] be until it dies, and then check the gullet from the inside.15I.e., he should cut the gullet off at its top and/or bottom and turn it inside out. If he is able to find a drop of blood, he can assume that it is perforated and it is unacceptable. An external examination of the gullet is not sufficient for the surface of the gullet is red and a drop of blood will not be noticeable. Its inner surface, however, is skin-colored and the blood will be noticed (Kessef Mishneh). If a drop of blood was not found on it, it is apparent that it was not perforated and it is acceptable.

הלכה ט
חֲלָדָה כֵּיצַד. כְּגוֹן שֶׁהִכְנִיס הַסַּכִּין בֵּין סִימָן לְסִימָן. בֵּין שֶׁפָּסַק הַסִּימָן הָעֶלְיוֹן לְמַעְלָה בֵּין שֶׁשָּׁחַט הַתַּחְתּוֹן לְמַטָּה שֶׁהוּא דֶּרֶךְ שְׁחִיטָה הֲרֵי זוֹ פְּסוּלָה:
כסף משנה
9.
What is meant by chaladah?16Chullin 20b states that this term is derived from the word chuldah meaning "weasel," i.e., an animal that hides in the foundation of homes. Similarly, chaladah involves "hiding" the knife when slaughtering; i.e., inserting it in a way that the blade is not open to the eye. Implied is that the proper way to slaughter is for the slaughterer to hold the animal or fowl with its neck upward and to draw the knife back and forth across the neck. For example, one inserted the knife between one sign and another.17Certainly, this applies when he inserted the knife below both signs and slaughtered the animal by moving the knife back and forth while pointed upward (Siftei Cohen 24:6). Whether one then slits the upper sign above or cuts the lower sign below in the manner of ritual slaughter, [the slaughter] is unacceptable.

הלכה י
הִכְנִיס אֶת הַסַּכִּין תַּחַת הָעוֹר וְשָׁחַט שְׁנֵי הַסִּימָנִים כְּדַרְכָּן. אוֹ שֶׁהֶחְלִיד אֶת הַסַּכִּין תַּחַת צֶמֶר מְסֻבָּךְ. אוֹ שֶׁפָּרַס מַטְלִית עַל הַסַּכִּין וְעַל הַצַּוָּאר וְשָׁחַט תַּחַת הַמַּטְלִית הוֹאִיל וְאֵין הַסַּכִּין גְּלוּיָה הֲרֵי זוֹ סְפֵק נְבֵלָה. וְכֵן אִם שָׁחַט מִעוּט הַסִּימָנִים בְּהַחְלָדָה וְגָמַר הַשְּׁחִיטָה שֶׁלֹּא בְּהַחְלָדָה הֲרֵי זוֹ סְפֵק נְבֵלָה:
כסף משנה
10.
If he inserted the knife beneath the [animal's] skin and slit both the signs in the ordinary fashion, hid the knife under tangled wool, or spread a cloth over the knife and the neck18In his Kessef Mishneh, Rav Yosef Caro quotes other authorities who explain that this is referring to a situation where the person tied the cloth around the animal's neck, attached it with wax, or the like. If, however, he merely loosely spread the cloth over the animal, the slaughter is acceptable. He concludes, however, that the Rambam's opinion should be respected. In his Shulchan Aruch (Yoreh De'ah 24:8), he rules according to the other views, but states: "One should show concern for his (the Rambam's) opinion at the outset." and slaughtered under the cloth, since the knife is not openly revealed, there is an unresolved doubt whether [the animal is considered] a nevelah. Similarly, if slaughtered less than half the signs with chaladah and completed the slaughter without chaladah, there is an unresolved doubt whether [the animal is considered] a nevelah.

הלכה יא
דְּרָסָה כֵּיצַד. כְּגוֹן שֶׁהִכָּה בְּסַכִּין עַל הַצַּוָּאר כְּדֶרֶךְ שֶׁמַּכִּין בְּסַיִף וְחָתַךְ הַסִּימָנִין בְּבַת אַחַת בְּלֹא הוֹלָכָה וְלֹא הוֹבָאָה. אוֹ שֶׁהִנִּיחַ הַסַּכִּין עַל הַצַּוָּאר וְדָחַק וְחָתַךְ לְמַטָּה כְּחוֹתֵךְ צְנוֹן אוֹ קִישׁוּת עַד שֶׁחָתַךְ הַסִּימָנִין הֲרֵי זוֹ פְּסוּלָה:
כסף משנה
11.
What is meant by dirasah?19The term doreis means "prey" or "strike," i.e., killing with a blow, rather than drawing back and forth as is required for ritual slaughter. For example, one struck the neck with a knife as one strikes with a sword, cutting the signs at one time, without passing [the knife] back and forth or one placed the knife on the neck and pressed, cutting downward like one cuts radishes or squash until he cuts the signs, [the slaughter] is unacceptable.

הלכה יב
הַגְרָמָה כֵּיצַד. זֶה הַשּׁוֹחֵט בַּקָּנֶה לְמַעְלָה בְּמָקוֹם שֶׁאֵינוֹ רָאוּי לִשְׁחִיטָה. וּכְמוֹ שְׁנֵי חִטִּים יֵשׁ בְּסוֹף הַקָּנֶה לְמַעְלָה בְּטַבַּעַת גְּדוֹלָה. שָׁחַט בְּתוֹךְ הַחִטִּים אִם שִׁיֵּר מֵהֶן כָּל שֶׁהוּא לְמַעְלָה הֲרֵי זוֹ כְּשֵׁרָה. שֶׁהֲרֵי שָׁחַט מִשִּׁפּוּי כּוֹבַע וּלְמַטָּה. וְהוּא מִן הַמָּקוֹם הָרָאוּי לִשְׁחִיטָה. וְאִם לֹא שִׁיֵּר מֵהֶן כְּלוּם אֶלָּא שָׁחַט לְמַעְלָה מֵהֶן הֲרֵי זוֹ מֻגְרֶמֶת וּפְסוּלָה:
כסף משנה
12.
What is meant by hagramah?20The Maggid Mishneh gives two interpretations of the term hagramah:
a) "lift up," as in II Kings 9:13; i.e., he lifted the knife above its proper place; and
b) "tip," as in Bava Batra 88b; i.e., he tipped the knife upward.
This refers to one who slaughters at a high point on the windpipe21The Rambam speaks only with regard to the windpipe, because he defines hagramah as slaughtering the animal in an improper place. If one would slit the gullet above the proper place, the animal would become disqualified as a trefe immediately (Kessef Mishneh). where it is not fit to slaughter. There are two [nodes, like kernels of] wheat at the top of the windpipe, at the large ring.22The Maggid Mishneh states that the windpipe is made up of many rings. Over the top ring, there is a flap (cap) of flesh which is slanted. (This is the area of the larynx. See also Chapter 1, Halachah 7, and notes.) At the top of this flap, there are two kernel-like buttons of flesh. As long as the slaughterer leaves some portion of these kernels intact, the slaughter is acceptable. [The following rules apply if] one slaughtered in the midst of these kernels. If he left even the slightest portion of them intact above [the place of slaughter], it is acceptable, for he slaughtered from the slanting cap [of the windpipe] or lower. This is within the place that is fit for ritual slaughter. If, however, he did not leave any portion of them intact, but instead cut above them, this is considered as [being slaughtered with] hagramah and it is unacceptable.

הלכה יג
שָׁחַט רֹב הָאֶחָד אוֹ רֹב הַשְּׁנַיִם וְהִשְׁלִים הַשְּׁחִיטָה בִּדְרָסָה אוֹ בְּהַגְרָמָה הֲרֵי זוֹ כְּשֵׁרָה שֶׁהֲרֵי נִשְׁחַט הַשִּׁעוּר כָּרָאוּי. הִגְרִים בַּתְּחִלָּה שְׁלִישׁ וְשָׁחַט שְׁנֵי שְׁלִישִׁים הֲרֵי זוֹ כְּשֵׁרָה. שָׁחַט שְׁלִישׁ וְהִגְרִים שְׁלִישׁ וְחָזַר וְשָׁחַט שְׁלִישׁ הָאַחֲרוֹן כְּשֵׁרָה. הִגְרִים שְׁלִישׁ וְשָׁחַט שְׁלִישׁ וְחָזַר וְהִגְרִים שְׁלִישׁ הָאַחֲרוֹן הֲרֵי זוֹ פְּסוּלָה. וְאִם דָּרַס אוֹ הֶחְלִיד בֵּין בַּשְּׁלִישׁ הָרִאשׁוֹן בֵּין בַּשְּׁלִישׁ הָאֶמְצָעִי הֲרֵי זוֹ פְּסוּלָה:
כסף משנה
13.
If one slit the majority of one sign [for a fowl] or the majority of both signs [for an animal] and then completed the slaughter through dirasah or hagramah, it is acceptable, for the minimum measure was slaughtered in the proper manner.23The Rambam derived this concept from a comparison to the laws of shehiyah mentioned in Halachah 5. The same concept applies if one slaughters more than half the signs appropriately and then completes the slaughter through chaladah. Indeed, it can be explained that the Rambam does not mention this law with regard to chaladah, because it is obvious. For in chaladah, the slaughter is essentially correct; it is only the manner in which one inserts the knife that is unacceptable (Kessef Mishneh).
As mentioned in the notes to Halachah 5, there are opinions who differ and disqualify the slaughter. Similarly, with regard to the laws at hand, there are opinions that are more stringent, except with regard to hagramah. In that instance, they accept the leniency mentioned by the Rambam. The Shulchan Aruch (Yoreh De'ah 24:12) quotes both of the views without stating which should be followed. The Rama goes further and states that it is customary to rule stringently even with regard to hagramah, and even with regard to fowl.

If at first, he slit a third [of the windpipe]24This addition is necessary, for as stated above, if the gullet is perforated, the slaughter is disqualified. through hagramah, and then cut two thirds in the appropriate manner, the slaughter is acceptable.25For the majority of the windpipe was cut in an acceptable manner and the preliminary cutting did not cause the animal to be considered as a trefe. If he cut a third in the appropriate manner, cut a third through hagramah, and then cut the last third in the appropriate manner, the slaughter is acceptable.26Here also, the majority of the windpipe is cut in an acceptable manner. The fact that the two thirds were not cut directly after each other is not significant. If at first, he slit a third through hagramah, cut a third in the appropriate manner, and then cut a third through hagramah, the slaughter is unacceptable.27For the majority of the windpipe has not been slit in an acceptable manner. If one cut [a portion of] an animal's throat with derisah or chaladah, it is unacceptable, whether it was the first or second third.28The rationale for the Rambam's words has been discussed at length by the commentaries, because with regard to chaladah, in Halachah 10, he writes that there is an unresolved question whether the slaughter is disqualified, while here he appears to say that it is definitely unacceptable. The Rivosh (Responsum 187), the Kessef Mishneh, the Maggid Mishneh, and the Siftei Cohen 24:18 all offer lengthy - and somewhat forced - explanations to attempt to resolve the apparent contradiction. The core of the explanation of the Kessef Mishneh is that since the majority of the windpipe was slit in the proper place, it is not disqualified because a portion was not.
Needless to say, if one cuts the last third in either of these fashions, according to the Rambam, the slaughter is not disqualified, for it has already been completed (through slitting more than half of the sign[s] in an acceptable manner). The Rama, however, would disqualify the slaughter as stated above.

הלכה יד
עִקּוּר כֵּיצַד. כְּגוֹן שֶׁנֶּעֶקְרָה הַגַּרְגֶּרֶת וְהִיא הַקָּנֶה אוֹ הַוֵּשֶׁט וְנִשְׁמַט אֶחָד מֵהֶן אוֹ שְׁנֵיהֶן קֹדֶם גְּמַר שְׁחִיטָה. אֲבָל אִם שָׁחַט אֶחָד בָּעוֹף אוֹ רֻבּוֹ וְאַחַר כָּךְ נִשְׁמַט הַסִּימָן הַשֵּׁנִי שְׁחִיטָתוֹ כְּשֵׁרָה:
כסף משנה
14.
What is meant by ikur? That the gullet and/or the windpipe were displaced29The term ikur means "uproot." The Kessef Mishneh states that, according to the Rambam, the fact that the signs have slipped from their place does not cause the animal to be deemed a trefe (see, however, Chapter 9, Halachah 21, and notes). Nevertheless, such a condition disqualifies the animal, for it is impossible for the ritual slaughter to be carried out in the proper manner. and slid [from their place] before the conclusion of the slaughter. If, however, one slit an entire sign or its majority in a fowl, and then the second sign slipped, the slaughter is acceptable.30For the slaughter was already completed in an acceptable manner. Compare to the following halachah.

הלכה טו
נִשְׁמַט אֶחָד מֵהֶן וְאַחַר כָּךְ שָׁחַט אֶת הַשֵּׁנִי שְׁחִיטָתוֹ פְּסוּלָה. שָׁחַט אֶחָד מֵהֶן וְנִמְצָא הַשֵּׁנִי שָׁמוּט וְאֵין יָדוּעַ אִם קֹדֶם שְׁחִיטָה נִשְׁמַט אוֹ אַחַר שְׁחִיטָה הֲרֵי זוֹ סְפֵק נְבֵלָה:
כסף משנה
15.
If one of the signs was displaced and afterwards, one slit the other, the slaughter is unacceptable.31This applies even with regard to a fowl. Although it is only necessary for one of the signs of a fowl to be cut in the appropriate manner, the other one must be fit to be slit in an appropriate manner (Kessef Mishneh). If one slit one of the signs [of a fowl] and then discovered that the other one was displaced, but it is unknown whether it was displaced before slaughter32In which instance it would disqualify it. or after slaughter,33In which instance, it would be acceptable. there is an unresolved question whether [the fowl] is a nevelah.

הלכה טז
נִמְצָא הַסִּימָן הַשָּׁחוּט שָׁמוּט הֲרֵי זוֹ כְּשֵׁרָה. שֶׁוַּדַּאי אַחַר שְׁחִיטָה נֶעֱקַר. שֶׁאִלּוּ נֶעֱקַר קֹדֶם שְׁחִיטָה הָיָה מִתְדַּלְדֵּל וְלֹא נִשְׁחָט:
כסף משנה
16.
If the sign that was cut for ritual slaughter is discovered to have been displaced, [the fowl or animal]34With regard to a fowl, the sign in question is the only sign slit. With regard to an animal, the other sign must have been slaughtered effectively. is acceptable, for certainly, it was displaced after the slaughter. For if it had been displaced before ritual slaughter, it would have hung loosely and it would not have been able to be slaughtered [effectively].35The Tur and the Shulchan Aruch (Yoreh De'ah 24:18) rule more stringently and maintain that it is necessary to slaughter another animal, displace its signs afterwards, and compare the two. Only if they are similar is the slaughter accepted. Moreover, the Shulchan Aruch continues stating that, at present, we are not expert at making this comparison and hence, forbid an animal whenever such a condition arises.

הלכה יז
בַּמֶּה דְּבָרִים אֲמוּרִים שֶׁלֹּא תָּפַס הַסִּימָנִין בְּיָדוֹ כְּשֶׁשָּׁחַט. אֲבָל אִם תְּפָסָן וְשָׁחַט אֶפְשָׁר שֶׁתִּשָּׁחֵט אַחַר הָעִקּוּר וּלְפִיכָךְ אִם נִמְצֵאת שְׁמוּטָה וּשְׁחוּטָה הֲרֵי זוֹ סְפֵק נְבֵלָה:
כסף משנה
17.
When does the above apply? When [the slaughterer] did not hold the signs in his hand when he slit them. If, however, he held the signs and slaughtered, it is possible that [the signs] could have been slit [effectively even] after they were displaced.36Because the slaughterer will hold the signs in the proper position by hand. Therefore, if a sign is discovered to be displaced and slaughtered,37And we do not know whether the slaughterer held it by hand or not. there is an unresolved question whether [the animal or the fowl] is a nevelah.

הלכה יח
כָּל מָקוֹם שֶׁאָמַרְנוּ בִּשְׁחִיטָה פְּסוּלָה הֲרֵי זוֹ נְבֵלָה. וְאִם אָכַל מִמֶּנָּה כְּזַיִת לוֹקֶה מִשּׁוּם אוֹכֵל נְבֵלָה שֶׁאֵין מוֹצִיא מִידֵי נְבֵלָה אֶלָּא שְׁחִיטָה כְּשֵׁרָה כַּאֲשֶׁר צִוָּה משֶׁה רַבֵּנוּ עָלָיו הַשָּׁלוֹם כְּמוֹ שֶׁבֵּאַרְנוּ. וְכָל סָפֵק בִּשְׁחִיטָה הֲרֵי הוּא סְפֵק נְבֵלָה וְהָאוֹכֵל מִמֶּנָּה מַכִּין אוֹתוֹ מַכַּת מַרְדּוּת:
כסף משנה
18.
Whenever we have used the term "unacceptable," the animal is a nevelah and if a person partakes of an olive-sized portion of it, he is liable for lashes for partaking of a nevelah. For only an acceptable slaughter as commanded by Moses our teacher of blessed memory prevents an animal from being considered a nevelah as we explained.38See Chapter 1, Halachot 1 and 4. Whenever there is an unresolved doubt whether slaughter [is acceptable], there is an unresolved doubt whether the animal is a nevelah.39Since an animal is forbidden during its lifetime, its meat is permitted only when we are certain that the slaughter was acceptable (Radbaz). A person who partakes of it is liable for stripes for rebellious conduct.

הלכה יט
בְּהֵמָה שֶׁנִּטַּל יָרֵךְ שֶׁלָּהּ וַחֲלָלָה עִמָּהּ עַד שֶׁתֵּרָאֶה חֲסֵרָה כְּשֶׁתִּרְבַּץ הֲרֵי זוֹ נְבֵלָה כְּמוֹ שֶׁנֶּחְתַּךְ חֶצְיָהּ וְנֶחְלְקָה לִשְׁנֵי גּוּפוֹת וְאֵין הַשְּׁחִיטָה מוֹעֶלֶת בָּהּ. וְכֵן אִם נִשְׁבְּרָה מִפְרֶקֶת וְרֹב בָּשָׂר עִמָּהּ אוֹ שֶׁנִּקְרְעָה מִגַּבָּהּ כְּדָג אוֹ שֶׁנִּפְסַק רֹב הַקָּנֶה אוֹ שֶׁנִּקַּב הַוֵּשֶׁט בְּכָל שֶׁהוּא בְּמָקוֹם הָרָאוּי לִשְׁחִיטָה הֲרֵי זוֹ נְבֵלָה מֵחַיִּים וְאֵין הַשְּׁחִיטָה מוֹעֶלֶת בָּהּ. וְאֶחָד הַבְּהֵמָה וְאֶחָד הָעוֹף בְּכָל הַדְּבָרִים הָאֵלֶּה:
כסף משנה
19.
When the thigh of an animal and [the meat40The addition is made on the basis of the gloss of the Maggid Mishneh. of] its hollow were removed and thus it appears lacking when it crouches, it is a nevelah.41I.e., even though the animal still has a certain vestige of vitality, it is considered as if it has died already and it imparts ritual impurity as a nevelah does (Hilchot Shaar Avot HaTumah 2:1). [It is] as if half of it was cut away and it was divided into two bodies. Thus slaughter is not effective with regard to it.
Similarly, if [the animal's] backbone was broken together with the majority of the meat, its back was ripped open like a fish, the majority of the windpipe was been severed,42In this and the following instance, the Siftei Cohen 33:4 rules that the animal is a trefe and not a nevelah. or the gullet was perforated in a place fit for slaughter,43If, however, the gullet was perforated at a higher point in the neck (see Halachah 12), it is considered as a trefe and not a nevelah. it is considered as a nevelah while alive and slaughter will not be effective with regard to it. The same laws apply to both an animal and a fowl with regard to all these matters.

הלכה כ
שְׁנֵי עוֹרוֹת יֵשׁ לוֹ לַוֵּשֶׁט. הַחִיצוֹן אָדֹם וְהַפְּנִימִי לָבָן. נִקַּב הָאֶחָד מֵהֶן בִּלְבַד כְּשֵׁרָה. נִקְּבוּ שְׁנֵיהֶן בְּכָל שֶׁהוּא בְּמָקוֹם הָרָאוּי לִשְׁחִיטָה הֲרֵי זוֹ נְבֵלָה. וּבֵין שֶׁנִּשְׁחֲטָה בִּמְקוֹם הַנֶּקֶב בֵּין שֶׁנִּשְׁחֲטָה בְּמָקוֹם אַחֵר אֵין הַשְּׁחִיטָה מוֹעֶלֶת בָּהּ. נִקְּבוּ שְׁנֵיהֶם זֶה שֶׁלֹּא כְּנֶגֶד זֶה נְבֵלָה:
כסף משנה
20.
The gullet has two membranes: the external membrane is red and the inner membrane is white.44I.e., skin-colored. If only one of them is perforated, [the animal] is acceptable.45For the one that is not perforated is sufficient to protect the animal sufficiently for it to survive.
This leniency applies when the inner membrane is perforated due to sickness. If, however, it is perforated due to a thorn, we fear that the outer membrane may also be perforated, but that perforation cannot be detected [see Halachah 22; Rama (Yoreh De'ah 33:4)].
If they are both perforated even to the slightest degree in a place fit for slaughter, it is a nevelah.46As above, if the gullet was perforated at a higher point in the neck (see Halachah 12), it is considered as a trefe and not a nevelah (Kessef Mishneh). [This applies] whether it was slaughtered in the place of the perforation or in another place, slaughter will not be effective with regard to it. If they were both perforated, [even when] one [hole] does not correspond to the other, the animal is a nevelah47With regard to other organs which have two membranes, e.g., the brain and the lungs, the animal is not considered as trefe unless the holes correspond to each other. In this instance, however, the ruling is much more severe because the gullet is stretched and becomes extended. Thus even if the place of the holes do not correspond, they can match each other at times [Kessef Mishneh, Shulchan Aruch (Yoreh De'ah 33:4)]..

הלכה כא
נִקַּב הַוֵּשֶׁט וְעָלָה בּוֹ קְרוּם וּסְתָמוֹ אֵין הַקְּרוּם כְּלוּם וַהֲרֵי הוּא נָקוּב כְּשֶׁהָיָה. נִמְצָא קוֹץ עוֹמֵד בַּוֵּשֶׁט הֲרֵי זוֹ סְפֵק נְבֵלָה שֶׁמָּא נִקַּב הַוֵּשֶׁט וְעָלָה קְרוּם בִּמְקוֹם הַנֶּקֶב וְאֵינוֹ נִרְאֶה. אֲבָל אִם נִמְצָא הַקּוֹץ לְאָרְכּוֹ בַּוֵּשֶׁט אֵין חוֹשְׁשִׁין לוֹ שֶׁרֹב הַבְּהֵמוֹת הַמִּדְבָּרִיּוֹת אוֹכְלוֹת הַקּוֹצִים תָּמִיד:
כסף משנה
21.
When the gullet is perforated and a scab forms which covers it, the scab is of no consequence and it is considered perforated as it was beforehand.48For as the gullet expands, it is possible that the scab will open (Rashi, Chullin 42a). If a thorn is detected standing in the gullet, there is an unresolved doubt whether the animal is a nevelah. We fear that perhaps a scab developed in the place of a perforation and it is not visible.49The Rama (Yoreh De'ah 33:9) rules more leniently, stating that unless a trace of blood is detected on the outer side, we do not disqualify an animal because a thorn was implanted in the gullet. If, however, a thorn is lying lengthwise50The Shulchan Aruch (Yoreh De'ah 33:9) rules that this applies even if the thorn is lying widthwise, as long as it is not implanted in the membrane. [Indeed, some versions of the Mishneh Torah substitute widthwise for lengthwise.] in the gullet, we are not concerned about it, for most desert animals eat thorns continuously.51And yet do not suffer any internal damage.

הלכה כב
וֵשֶׁט אֵין לוֹ בְּדִיקָה מִבַּחוּץ אֶלָּא מִבִּפְנִים. כֵּיצַד. הוֹפְכוֹ וּבוֹדֵק. אִם נִמְצָא עָלָיו טִפַּת דָּם בְּיָדוּעַ שֶׁהָיָה נָקוּב:
כסף משנה
22.
The gullet cannot be checked from the outside, only from the inside.52Because, as stated above (see Halachot 8, 19), since its outer membrane is red, a trace of blood will not be obvious. What is implied? One should turn it inside out and check it. If a drop of blood is found upon it, it can be concluded that it was perforated.

הלכה כג
גַּרְגֶּרֶת שֶׁנִּפְסַק רֹב חֲלָלָה בַּמָּקוֹם הָרָאוּי לִשְׁחִיטָה הֲרֵי זוֹ נְבֵלָה. וְכֵן אִם נִקְּבָה כְּאִיסָר. נִקְּבָה נְקָבִים קְטַנִּים אִם נְקָבִים שֶׁאֵין בָּהֶן חֶסְרוֹן הֵם מִצְטָרְפִין לְרֻבָּהּ וְאִם נְקָבִים שֶׁיֵּשׁ בָּהֶם חֶסְרוֹן מִצְטָרְפִין לִכְאִיסָר. וְכֵן אִם נִטְּלָה מִמֶּנָּה רְצוּעָה מִצְטָרֶפֶת לִכְאִיסָר. וּבְעוֹף כָּל שֶׁאִלּוּ מְקַפֵּל הָרְצוּעָה אוֹ הַנְּקָבִים שֶׁיֵּשׁ בָּהֶן חֶסְרוֹן וּמַנִּיחָן עַל פִּי הַקָּנֶה אִם חוֹפֶה אֶת רֻבּוֹ נְבֵלָה וְאִם לָאו כְּשֵׁרָה:
כסף משנה
23.
When the majority of the cavity of the windpipe53I.e., the slit goes from side to side in a manner in which the majority of the cavity is slit. The Rambam (based on Chullin 44a,b) is emphasizing that this measure disqualifies an animal even if when including the thickness of the flesh of the windpipe, the slit would not cover the majority of the windpipe. has been severed in the place fit for slaughtering,54See Chapter 1, Halachah 7, and notes. [the animal] is a nevelah. This also applies if it has a hole the size of an isar.55An Italian coin, frequently used in the Talmudic era. In his commentary to the Mishnah (Mikveot 9:5), the Rambam states that an isar is the weight of four barley corns.
The Shulchan Aruch (Yoreh De'ah 34:2) states that we are unfamiliar with the measure of an isar. Therefore, the laws applying to an animal should resemble those applying to a fowl and if the slit covers the majority of the cavity of the windpipe, it is disqualified. The Rama states that, for an animal, an isar is smaller than the majority of the cavity of the windpipe. Therefore he states that perhaps the intent of the Shulchan Aruch, is the majority of the cavity of a fowl. He cautions anyone who has a doubt to rule stringently and disqualify the animal.

[The following rules apply if the windpipe of an animal] was perforated with small holes.56When quoting this law, the Shulchan Aruch (Yoreh De'ah 33:3) speaks of perforating the windpipe "like a sifter." If the perforations did not detract [from the flesh, they disqualify the animal if,] when they are added together, they constitute the majority [of the windpipe]. If they detract from the flesh, [they disqualify the animal if,] when they are added together, their sum is the size of an isar.57In his Kessef Mishneh and his Shulchan Aruch (Yoreh De'ah 34:3), Rav Yosef Caro writes that as long as the flesh between the holes is not larger than the holes themselves, it is included together with them in this measure. Similarly, if a strand [of flesh] is removed from [the windpipe], it [disqualifies the animal if its area] is the size of an isar.
With regard to a fowl, [a more stringent rule applies]:58For the entire windpipe of a fowl may not be the size of an isar (Rashi, Chullin 45a). Whenever the strip [of flesh that was removed] or the holes that detract from the flesh [are large enough so that they] could be folded so that when placed over the opening of the windpipe, it would cover the majority [of its cavity],59The addition is based on the gloss of the Kessef Mishneh. For each particular fowl, this measure is calculated individually (Maggid Mishneh). it is a nevelah. If not, it is acceptable.

הלכה כד
נִקְּבָה הַגַּרְגֶּרֶת נֶקֶב מְפֻלָּשׁ מִשְּׁנֵי צְדָדֶיהָ כְּדֵי שֶׁיִּכָּנֵס אִיסָר לְרָחְבּוֹ נְבֵלָה. נִסְדְּקָה לְאָרְכָּהּ אֲפִלּוּ לֹא נִשְׁתַּיֵּר מִן הַמָּקוֹם הָרָאוּי בָּהּ לִשְׁחִיטָה אֶלָּא מַשֶּׁהוּ לְמַעְלָה וּמַשֶּׁהוּ לְמַטָּה כְּשֵׁרָה:
כסף משנה
24.
If the windpipe was perforated on both sides with a hole large enough for the thickness of isar60Our translation is based on the gloss of the Kessef Mishneh who quotes the Tur (Yoreh De'ah 34) who explains that in contrast to the previous halachah which speaks of a hole the area of an isar, this halachah is speaking about a hole through which an isar can be slipped through on its side.
It must be emphasized that the Rambam's ruling depends on the interpretation of Chullin 54a advanced by Rabbenu Yitzchak Alfasi. Rashi advances a different interpretation of that passage on which basis, the Ra'avad objects to the Rambam's ruling. The Shulchan Aruch (Yoreh De'ah 34:5-6) quotes both opinions without stating which is favored.
to be inserted into it, it is a nevelah. If it is slit lengthwise, even if only the slightest portion of the place fit to slaughter [an animal] remains above and below, it is acceptable.61The Kessef Mishneh quotes Rashi who explains that if the windpipe is slit across we rule more stringently, for the stress of breathing will extend the windpipe and cause the slit to expand. This does not apply when it is split lengthwise.

הלכה כה
גַּרְגֶּרֶת שֶׁנִּקְּבָה וְאֵין יָדוּעַ אִם קֹדֶם שְׁחִיטָה נִקְּבָה אוֹ אַחַר שְׁחִיטָה נִקְּבָה. נוֹקְבִין אוֹתָהּ עַתָּה בְּמָקוֹם אַחֵר וּמְדַמִּין הַנֶּקֶב לְנֶקֶב אִם נִדְמֶה לוֹ מֻתֶּרֶת. וְאֵין מְדַמִּין אֶלָּא מֵחֻלְיָא גְּדוֹלָה לְחֻלְיָא גְּדוֹלָה אוֹ מִקְּטַנָּה לִקְטַנָּה. אֲבָל לֹא מִקְּטַנָּה לִגְדוֹלָה שֶׁכָּל הַקָּנֶה חֻלְיוֹת חֻלְיוֹת הוּא וּבֵין כָּל חֻלְיָא וְחֻלְיָא חֻלְיָא אַחַת קְטַנָּה מִשְּׁתֵּיהֶן וְרַכָּה:
כסף משנה
25.
When a windpipe has been perforated62In a manner that would disqualify the animal. and it is not known whether it was perforated before the slaughter or afterwards,63Were it to have been perforated afterwards, the perforation would not be significant. we perforate it again in another place and compare the two holes. If they resemble each other, it is permitted.64For it is apparent that the first hole was also made after the animal's death. The Rama (Yoreh De'ah 34:9) states that we are not proficient in inspecting the animal in this way and should disqualify it in all situations.
We compare only [a hole in] a large ring to [a hole in] a large ring or [a hole in] a small [ring] to [a hole in] a small [ring], but not [a hole in] a small [ring] to a [a hole in] a large [ring]. For the entire windpipe is made up of a series of rings. Between each [large] ring is a small, soft ring.

קדושה הלכות שחיטה פרק ג
Kedushah Shechitah Chapter 3