Halacha

הלכה א
חֲסֵרָה כֵּיצַד. שְׁנֵי אֵיבָרִים הֵן שֶׁאִם חָסֵר מִמִּנְיָנָם טְרֵפָה. וְאֵלּוּ הֵן. הָרֵאָה וְהָרַגְלַיִם. וְחָמֵשׁ אֻנּוֹת יֵשׁ לָרֵאָה כְּשֶׁיִּתְלֶה אוֹתָהּ אָדָם בְּיָדוֹ וּפְנֵי רֵאָה כְּנֶגֶד פָּנָיו. שָׁלֹשׁ מִן הַיָּמִין. וּשְׁתַּיִם מִן הַשְּׂמֹאל. וּבְצַד יָמִין מִמֶּנָּה כְּמוֹ אֹזֶן קְטַנָּה וְאֵינָהּ בְּצַד הָאֻנּוֹת וְיֵשׁ לָהּ כְּמוֹ כִּיס בִּפְנֵי עַצְמָהּ וְהִיא בְּתוֹךְ הַכִּיס. וְאֹזֶן זוֹ קְטַנָּה הִיא הַנִּקְרָא וַרְדָּא מִפְּנֵי שֶׁהִיא דּוֹמָה לְוֶרֶד וְאֵינָהּ מִן הַמִּנְיָן. לְפִיכָךְ אִם לֹא נִמְצֵאת הַוַּרְדָּא מֻתֶּרֶת. שֶׁכָּךְ הִיא דַּרְכָּהּ יֵשׁ בְּהֵמוֹת תִּמָּצֵא בָּהֶם וְיֵשׁ בְּהֵמוֹת לֹא תִּמָּצֵא בָּהֶם. וְאִם נִמְצֵאת נְקוּבָה אַף עַל פִּי שֶׁהַכִּיס שֶׁלָּהּ סוֹתֵם אֶת הַנֶּקֶב הֲרֵי זוֹ טְרֵפָה:
כסף משנה
1.
What is meant by the term chasairah?1Chasairah means "lacking." This category disqualifies an animal if it lacks one of its fundamental organs. There are two organs that render [an animal] trefe if it is lacking the proper number. They are the lungs and the feet.2It is true that there are more organs that render an animal trefe if they are lacking. Nevertheless, the lack of these organs is not placed in this category. Instead, the organ is considered as nekuvah, "perforated." As stated in Chapter 6, Halachah 20, if the perforation of these organs will disqualify an animal, surely, it will be disqualified when the organs are lacking entirely.
The lungs have five lobes. When a person will drape them over his hand with the inner portion of the lung facing his face,3I.e., he will be holding the animal from behind. See Shulchan Aruch (Yoreh De'ah 35:2). there will be three [lobes] on the right and two on the left. In addition, at the right of [the lung], there is a small ear-like attachment. It is not in the row of the lobes. It has a pocket of its own and it is located in the pocket. This [attachment] is called a rose, because that is what it looks like.4I.e., it is small and red. It is not counted as one of the number of lobes.
Accordingly, if [an animal] does not possess this "rose," it is permitted.5The Rama (Yoreh De'ah 35:2 states that it is customary within the Ashkenazic community to declare an animal trefe, if it lacks this "rose" or if there is an extra "rose." For this is the pattern with regard to [this organ], there are some animals in which it is found and some in which it is not found. If it is perforated, [the animal] is trefe even though its pocket seals it.6For it does not seal it thoroughly.

הלכה ב
חָסֵר מִנְיַן הָאֻנּוֹת וְנִמְצֵאת אַחַת מִן הַשְּׂמֹאל אוֹ שְׁתַּיִם מִן הַיָּמִין טְרֵפָה. וְאִם נִמְצְאוּ שְׁתַּיִם בְּיָמִין וְזֹאת הַוַּרְדָּא הֲרֵי זוֹ מֻתֶּרֶת:
כסף משנה
2.
If the number of lobes was lacking and one was discovered on the left side or two on the right side, [the animal] is trefe. If, however, there were two on the right side and this "rose," [the animal] is permitted.7For the "rose" functions in place of the missing lobe. If, however, the "rose" is found on the left and there is only one lobe, the animal is not acceptable. Since it is not in its proper place, it cannot replace a lobe (Kessef Mishneh). The Shulchan Aruch (Yoreh De'ah 35:7) quotes the Rambam's ruling, but the Rama differs.

הלכה ג
נִתְחַלְּפוּ הָאֻנּוֹת וְנִמְצְאוּ שָׁלֹשׁ מִן שְׂמֹאל וּשְׁתַּיִם מִן הַיָּמִין בְּלֹא וֶרֶד. אוֹ שֶׁהָיָה הַוֶּרֶד עִם הַשָּׁלֹשׁ בְּצַד שְׂמֹאל. הֲרֵי זוֹ טְרֵפָה שֶׁהִיא חֲסֵרָה מִצַּד הַיָּמִין:
כסף משנה
3.
If the position of the lobes was switched and three were found on the left and two on the right without a "rose" or the "rose" was found together with three on the left side, it is trefe, for it is lacking on the right side.8In this instance, the "rose" does not compensate for the lack of the lobe, because it is not on the right side.

הלכה ד
נִתְוַסְּפוּ הָאֻנּוֹת בְּמִנְיָנָם אִם הָיְתָה הָאֹזֶן הַיְתֵרָה בְּצַד הָאֻנּוֹת אוֹ מִלִּפְנֵי הָרֵאָה שֶׁהוּא לְעֻמַּת הַלֵּב מֻתֶּרֶת. וְאִם הָיְתָה עַל גַּבָּהּ שֶׁהוּא לְעֻמַּת הַצְּלָעוֹת הֲרֵי זוֹ טְרֵפָה שֶׁהַיָּתֵר כְּחָסֵר. וְהוּא שֶׁתִּהְיֶה כְּמוֹ עָלֶה שֶׁל הֲדַס. אֲבָל פָּחוֹת מִזֶּה אֵינָהּ אֹזֶן וּמֻתֶּרֶת:
כסף משנה
4.
[The following rules apply if] the number of lobes was increased. If the extra lobe was on the side of the [other] lobes9"In the row of the lungs" to borrow the expression used by Chullin 47b. Generally, we follow the principle that every addition is considered as if it was lacking. In this instance, however, since the extra lobe is found in the row of the lobes, it will not disturb the lungs' ordinary functioning. or in front of the lungs10In this instance as well, the Rambam maintains that the position of the extra lobe prevents it from disturbing the lungs' ordinary functioning. The Shulchan Aruch (Yoreh De'ah 35:3) accepts the Rambam's ruling.The Rama quotes more stringent views that state that any extra lobe that is not found in the row of the lungs is trefe. Nevertheless, the custom is to rule leniently. on the side of the heart, [the animal] is permitted. If [the extra lobe] is on its back, near the ribs, [the animal] is trefe for an extra [organ] is considered equivalent to one that is lacking. [This applies] provided it is [at least] the size of a myrtle leaf.11I.e., even when inflated. If it is smaller than this, it is not considered as a lobe and [the animal] is permitted.

הלכה ה
אֹזֶן שֶׁנִּמְצֵאת דְּבוּקָה בַּחֲבֶרְתָּהּ הַסְּמוּכָה לָהּ מֻתֶּרֶת. וְאִם נִסְמְכוּ שֶׁלֹּא עַל הַסֵּדֶר כְּגוֹן שֶׁנִּסְמְכָה רִאשׁוֹנָה לַשְּׁלִישִׁית טְרֵפָה:
כסף משנה
5.
When one lobe is found clinging to the one next to it, [the animal] is permitted. If, however, [the lobes] became attached out of the ordinary order, e.g., the first lobe became attached to the third, [the animal] is trefe.12If the portions of the lungs that follow their natural pattern become attached to each other, all authorities agree that the animal is acceptable, for this attachment will not create any difficulties. And if the third lobe becomes attached to the first, all agree that it is unacceptable, because as the lungs inflate, the attached portions will separate, cause the attachment to tear, and in doing so, perforate the lobe.
The commentaries question - and the Maggid Mishneh actually maintains that the text of the Mishneh Torah reads in this manner - whether if the back of one lobe is attached to the back of the lobe next to it, the animal is also trefe. For in this instance as well, since the lobes are attached in an unnatural order, the attachment will tear and perforate the lungs. In his Kessef Mishneh, Rav Yosef Caro maintains that the Rambam's wording implies that as long as the attached lobes are next to each other, the lung is acceptable, even if they are attached back to back. He does note, however, that there are authorities who rule stringently. He concludes in his Kessef Mishneh and also rules accordingly in his Shulchan Aruch (Yoreh De'ah 39:4), that the attachments do not disqualify an animal only when the lobes are attached side to side - and not back to back - in the natural order. If they are attached in such an order, however, the lungs need not be checked. The Rama differs, requiring an examination. He also states that there are authorities who maintain that we are not knowledgable regarding how to make such an examination and therefore such an animal should be considered as trefe. Nevertheless, his ruling also leaves room for leniency if less than half of the body of the lobes are attached. See Siftei Cohen 39:11.

הלכה ו
נִמְצְאוּ שְׁתֵּי הָאֻנּוֹת כְּאֻנָּה אַחַת וְאֵינָן נִרְאוֹת כִּשְׁתַּיִם דְּבוּקוֹת אִם הָיָה בֵּינֵיהֶן כְּמוֹ עֲלֵה הַהֲדַס בֵּין בְּעִקָּרָן בֵּין בְּאֶמְצָעָן בֵּין בְּסוֹפָן כְּדֵי שֶׁיֻּכַּר שֶׁהֵן שְׁתַּיִם דְּבוּקוֹת מֻתֶּרֶת וְאִם לָאו הֲרֵי זוֹ חֲסֵרָה וּטְרֵפָה:
כסף משנה
6.
[The following laws apply if] there are two lobes [that appear] as one lobe and do not appear as two lobes joined together.13I.e., they appear as one flush mass, without differentiation. If they are distinct, but attached, they are governed by the laws stated in the previous halachah. If there was a space about the size of a myrtle leaf14From Halachah 4, it appears that this is the size of a lobe that is significant. Hence, just as it is significant in disqualifying an animal, it is significant in causing it to be deemed kosher (Maggid Mishneh).
The Rambam's ruling is quoted by the Shulchan Aruch (Yoreh De'ah 35:8). The Rama cites authorities that maintain that even if a smaller portion is distinct, the lobes are considered as separate and the animal, kosher. The Rama states that we may rely on these opinions if there is a significant loss involved.
between them - whether at their root, in their center, or at their end - so that it is clear that they are two which are attached, [the animal] is permitted. If not, it is lacking [one of the lobes] and is trefe.

הלכה ז
נִמְצֵאת כֻּלָּהּ שְׁתֵּי עֲרוּגוֹת וְאֵין לָהּ חִתּוּךְ אָזְנַיִם טְרֵפָה. וְכֵן אִם חָסֵר גּוּף הָרֵאָה אַף עַל פִּי שֶׁלֹּא נִקְּבָה הֲרֵי זוֹ כְּמִי שֶׁחָסֵר מִנְיַן הָאֻנּוֹת וּטְרֵפָה. לְפִיכָךְ אִם נִמְצָא מִמֶּנָּה מָקוֹם יָבֵשׁ עַד שֶׁיִּפָּרֵךְ בְּצִפֹּרֶן הֲרֵי זוֹ כְּחָסֵר וּטְרֵפָה וַאֲפִלּוּ הָיָה כָּל שֶׁהוּא:
כסף משנה
7.
If the entire lung appears like two rows and it is not divided into lobes, it is trefe. Similarly, if the body of the lung itself15I.e., it is lacking part of its ordinary mass. was lacking, even if it was not perforated, it is considered as if the required number of lobes were missing and [the animal] is trefe.16The Kessef Mishneh notes that in Chapter 7, Halachah 9, the Rambam rules that if a lung has decayed, it is kosher as long as its bronchioles and outer membrane are intact despite the fact that it has lost a large amount of its substance. He explains that this is not necessarily a contradiction to the ruling here. In that instance, since the lung has decayed significantly and yet, the brochioles have not been perforated, we assume that they will not be perforated. In this instance, by contrast, we suspect that the lack within the lung will cause it to become perforated.
Many other Rishonim, however, do not make such a distinction and maintain that a lung is acceptable if it is lacking some of its inner substance. The Shulchan Aruch (Yoreh De'ah 36:8) quotes both views. The Rama states that certain circumstances call for leniency and others, for stringency.
Therefore if a dried portion that could be chipped away with one's nail of even the slightest size was discovered within it, it is considered as lacking17The Kessef Mishneh explains that others explain that it is considered as if the dried portion is perforated and therefore the animal is trefe. and [the animal] is trefe.

הלכה ח
רֵאָה שֶׁנִּמְצֵאת נְפוּחָה כְּמוֹ עִקַּר חֲרָיוֹת שֶׁל דֶּקֶל אוֹסְרִין אוֹתָהּ מִסָּפֵק. שֶׁזּוֹ תּוֹסֶפֶת מְשֻׁנָּה בְּגוּפָהּ וְשֶׁמָּא הַתּוֹסֶפֶת בַּגּוּף כְּחִסָּרוֹן כְּמוֹ שֶׁאָמַר בְּמִנְיָן:
כסף משנה
8.
When a lung was discovered to be inflated like the leaves of a palm tree, we rule that it is forbidden because of the doubt involved. For this is an abnormal addition to its body and perhaps an addition to its body is considered as equivalent to a lack in its body, as stated with regard to the number of lobes.18As stated in law 4, an extra lobe is considered as a missing lobe and disqualifies a lung. Similarly, there is reason to think that an increase in the size of a lung is equivalent to a decrease in its size and disqualifies it in a similar fashion.

הלכה ט
הַבְּהֵמָה שֶׁפָּחֲדָה וְיָרְאָה עַד שֶׁצָּמְקָה הָרֵאָה שֶׁלָּהּ וְקָרְבָה לִהְיוֹת יְבֵשָׁה. אִם פָּחֲדָה בִּידֵי שָׁמַיִם כְּגוֹן שֶׁשָּׁמְעָה קוֹל רַעַם אוֹ רָאֲתָה זִקִּים וְכַיּוֹצֵא בָּזֶה מֻתֶּרֶת. וְאִם פָּחֲדָה בִּידֵי אָדָם כְּגוֹן שֶׁשָּׁחֲטוּ לְפָנֶיהָ בְּהֵמָה אַחֶרֶת וְכַיּוֹצֵא בָּזֶה הֲרֵי זוֹ כַּחֲסֵרָה וּטְרֵפָה:
כסף משנה
9.
[The following rules apply when] an animal became frightened and was terrified to the extent that her lung19When quoting this law, Shulchan Aruch (Yoreh De'ah 36:14) speaks of an "entire lung" shriveling. shriveled and came closer to becoming dried out: If it became frightened through the hand of heaven, e.g., it heard a thunderclap, saw lightening, or the like, it is permitted.20For in the near future, it will regain its natural size, as indicated by the following halachah. If it became frightened through human activity, e.g., another animal was slaughtered in its presence or the like, it is considered as if it were lacking and it is trefe.

הלכה י
כֵּיצַד בּוֹדְקִין אוֹתָהּ. מוֹשִׁיבִין אֶת הָרֵאָה בְּמַיִם מֵעֵת לְעֵת. וְאִם הָיָה זְמַן הַקֹּר מוֹשִׁיבִין אוֹתָהּ בְּמַיִם פּוֹשְׁרִין וּבִכְלִי שֶׁאֵין הַמַּיִם מִתְמַצִּין מִגַּבּוֹ וְנֹזְלִים כְּדֵי שֶׁלֹּא יִצֹּנּוּ בִּמְהֵרָה. וְאִם הָיָה זְמַן הַחֹם מוֹשִׁיבִין אוֹתָהּ בְּמַיִם צוֹנֵן בִּכְלִי שֶׁהַמַּיִם מִתְמַצִּין מִגַּבּוֹ כְּדֵי שֶׁיִּשָּׁאֲרוּ קָרִים. אִם חָזְרָה לִבְרִיָּתָהּ הֲרֵי זוֹ בִּידֵי שָׁמַיִם וּמֻתֶּרֶת. וְאִם לֹא חָזְרָה בִּידֵי אָדָם הִיא וּטְרֵפָה:
כסף משנה
10.
How do we inspect it? We place the lung in water for an entire day. In the winter, we place it in lukewarm water, in a container which will not cause the water to condense on its back21Chullin 55b states that earthern-ware utensils made of white clay will have water condense upon them easily. and flow so that they will not become cold rapidly. If the season was hot, we place it in cold water in a container on which the water will condense on its back so that the water will remain cold. If [the lung] returns to its natural state, [we assume that the animal was frightened] by the hand of heaven and it is permitted.22Chullin, loc. cit., also debates what the ruling would be if one animal is frightened by another animal. The Rambam does not discuss the issue for seemingly, it would be able to be resolved by the same test mentioned here. The Shulchan Aruch (Yoreh De'ah 36:14 considers being frightened by other animals as equivalent to being frightened by the hand of heaven.
The Radbaz also states that if the lung returns to normal, it is acceptable even if the animal was frightened by human activity. Other authorities differ and maintain that if we know that the animal was frightened by human activity, this examination is not acceptable (Siftei Cohen 36:30).
See also Rama (Yoreh De'ah 36:15) who rules that in the present era, we are not knowledgeable with regard to the various inspections that our Sages spoke about and hence, should not employ them. If, however, it appears that an animal's lung shrunk due to the hand of heaven, it should not be permitted without undergoing this examination.
If it does not return, we [we assume that] it happened due to mortal causes and [the animal] is trefe.

הלכה יא
בְּהֵמָה שֶׁהָיְתָה חֲסֵרָה רֶגֶל בִּתְחִלַּת בְּרִיָּתָהּ טְרֵפָה. וְכֵן אִם הָיְתָה יְתֵרָה רֶגֶל. שֶׁכָּל הַיָּתֵר כְּחָסֵר הוּא. אֲבָל אִם הָיוּ לָהּ שָׁלֹשׁ יָדַיִם אוֹ יד אַחַת מֻתֶּרֶת. לְפִיכָךְ אִם נֶחְתַּךְ הַיָּד שֶׁלָּהּ מֻתֶּרֶת. נֶחְתַּךְ הָרֶגֶל מִן הָאַרְכֻּבָּה וּלְמַעְלָה טְרֵפָה. מִן הָאַרְכֻּבָּה וּלְמַטָּה מֻתֶּרֶת. בְּאֵי זוֹ אַרְכֻּבָּה אָמְרוּ בְּאַרְכֻּבָּה שֶׁהוּא סוֹף הַיָּרֵךְ הַסָּמוּךְ לַגּוּף:
כסף משנה
11.
An animal that was lacking a foot23The category of chasairah involves two organs: the lungs and the feet. Having discussed the lungs, the Rambam proceeds to discuss the feet. As the Rambam continues to explain, here the intent is the hindlegs. from the time it came into being is trefe. The same ruling applies if it possesses an extra foot, for an extra limb or organ is considered as if it was lacking. If, however, it has three forefeet or only one forefoot, [the animal] is permitted. Accordingly, if [an animal's] forefoot is cut off, [the animal] is permitted.24The severed foot itself, however, is forbidden.
If its leg is cut off from the joint and above,25There are three segments of an animal's leg between its trunk and its hoofs. We are speaking about the joint between the highest and middle portions of the leg. [the animal] is trefe. From the joint and below, it is permitted.26Note, however, Halachah 15. Which joint are we speaking about? The joint that is at the end of the hip close to the body.

הלכה יב
נִשְׁבַּר הָעֶצֶם לְמַעְלָה מִן הָאַרְכֻּבָּה אִם יָצָא כֻּלּוֹ אוֹ רֻבּוֹ לַחוּץ הֲרֵי זֶה כְּמָה שֶׁנֶּחְתַּךְ וְנָפַל וּטְרֵפָה. וְאִם הָיָה הַבָּשָׂר אוֹ הָעוֹר חוֹפֶה רֹב עָבְיוֹ וְרֹב הֶקֵּפוֹ שֶׁל עֶצֶם שֶׁנִּשְׁבַּר הֲרֵי זוֹ מֻתֶּרֶת וַאֲפִלּוּ נָפַל מִקְצָת הָעֶצֶם שֶׁנִּשְׁבַּר וְהָלַךְ לוֹ. וְגִידִים הָרַכִּים אֵינָן חֲשׁוּבִין כְּבָשָׂר:
כסף משנה
12.
When the bone27I.e., the highest of the three bones of the animal's legs. is broken above the joint, if it emerges outward entirely or in its majority, it is considered as if it were cut and fell off,28For it will never heal. and [the animal] is trefe. If the flesh or the skin29Even the covering of the skin alone is sufficient. This represents a revision of the Rambam's thinking. The initial text of his Commentary to the Mishnah (Chullin 8:13) stated "there was flesh and skin covering it" and he altered it to read "flesh or skin covering it." was covering both the majority of the thickness and the majority of the circumference of the broken bone, [the animal] is permitted.30For the leg will heal. Not only is the animal permitted, the leg itself is permitted. We do not consider it as if it had been severed and removed during the animal's lifetime. This applies even if part of the broken bone fell off and no longer is present. Soft sinews are not considered as flesh.

הלכה יג
צֹמֶת הַגִּידִין הֵן בִּבְהֵמָה וּבְחַיָּה לְמַעְלָה מִן הֶעָקֵב בְּמָקוֹם שֶׁתּוֹלִין בּוֹ הַטַּבָּחִים הַבְּהֵמָה. וְהֵן שְׁלֹשָׁה גִּידִין לְבָנִים. אֶחָד עָבֶה וּשְׁנַיִם דַּקִּים. וּמִמָּקוֹם שֶׁיַּתְחִיל וְהֵן קָשִׁים וּלְבָנִים עַד שֶׁיָּסוּר הַלֹּבֶן מֵהֶן וְיַתְחִילוּ לְהִתְאַדֵּם וּלְהִתְרַכֵּךְ הוּא צֹמֶת הַגִּידִים. וְהוּא כְּאֹרֶךְ שֵׁשׁ עֶשְׂרֵה אֶצְבָּעוֹת בְּשׁוֹר:
כסף משנה
13.
The juncture of the sinews is a place in an animal and in a beast which is above the heel, at the place where the butchers hang the animal.31I.e., it is customary for the butchers to make a hole in the lowest bone of the leg and hang the animal head downwards so that they can skin it and cut off its meat. The definition of "the juncture of the sinews" is important, as reflected in Halachot 15-18. There are three white sinews there, one thick and two thin. From the place where they begin and are firm and white until [the place] where the whiteness is removed from them and they begin to become red and soften is considered the juncture of the sinews. It is approximately sixteen fingerbreadths32A fingerbreadth is approximately 2 cm according to Shiurei Torah and 2.4 cm according to Chazon Ish.
Together with the Rambam's view, the Shulchan Aruch (Yoreh De'ah 56:5) also quotes Rashi's view that the juncture of the sinews is four fingerbreadths long.
[long] in an ox.

הלכה יד
וּמִנְיַן גִּידִים אֵלּוּ בָּעוֹף שִׁשָּׁה עָשָׂר גִּידִין. תְּחִלָּתָן מִן הָעֶצֶם שֶׁל מַטָּה מֵאֶצְבַּע יְתֵרָה עַד סוֹף הָרֶגֶל שֶׁהוּא עָשׂוּי קַשְׂקַשִּׂים קַשְׂקַשִּׂים:
כסף משנה
14.
In a fowl, there are sixteen such sinews. They begin on the lowest bone, from the extra talon and [continue] until the conclusion of the foot which is [covered by a series of] crusted scales.33The Ra'avad takes issue with the Rambam's statements, admitting that the sinews of a fowl - as do those of an animal - begin in its actual feet. Nevertheless, he states, it is only from the joint between the second and third bone of the leg that they are considered halachically significant. For the laws of trefot that govern a fowl parallel those which govern an animal.
In his Kessef Mishneh, Rav Yosef Caro cites authorities that maintain that the text of the Mishneh Torah is in error and it should be amended to parallel the Ra'avad's comments. He cites a responsum attributed to the Rambam sent to the Sages of Provence which also follows this understanding. And in his Shulchan Aruch (Yoreh De'ah 56:8), he rules in this manner.

הלכה טו
בְּהֵמָה שֶׁנֶּחְתְּכוּ רַגְלֶיהָ בִּמְקוֹם צֹמֶת הַגִּידִין טְרֵפָה. וְאַל תִּתְמַהּ וְתֹאמַר כֵּיצַד תַּחְתֹּךְ לְמַעְלָה מִצֹּמֶת הַגִּידִים וְהִיא מֻתֶּרֶת עַד שֶׁתַּחְתֹּךְ לְמַעְלָה מִן הָאַרְכֻּבָּה הָעֶלְיוֹנָה כְּמוֹ שֶׁבֵּאַרְנוּ וְאִם נֶחְתַּךְ לְמַטָּה מִצֹּמֶת הַגִּידִים אֲסוּרָה. שֶׁבִּטְרֵפוֹת תַּחְתֹּךְ מִכָּאן וְתִחְיֶה וּמִכָּאן וְתָמוּת. וְלֹא נֶאֶסְרָה בְּהֵמָה זוֹ מִפְּנֵי שֶׁהִיא חֲתוּכַת רֶגֶל מִמָּקוֹם זֶה אֶלָּא מִפְּנֵי שֶׁנֶּחְתְּכוּ הַגִּידִין שֶׁחֲתִיכָתָן מִכְּלַל הַטְּרֵפוֹת כְּמוֹ שֶׁיִּתְבָּאֵר:
כסף משנה
15.
When an animal's feet are cut off at the juncture of the sinews, it is trefe. Do not be amazed and say: "How is it possible that [an animal] will be permitted if its [legs] are cut off above the juncture of the sinews - indeed, it is permitted unless its [legs] are cut off above the highest joint as we explained34Halachah 11.- but forbidden if they are cut off at a lower point, at the juncture of the sinews?
[The resolution is as follows: With regard to the designation of an animal] as trefe, [there are times when] one will cut from this point and it will live, but if [one would cut] from this point, it would die. We have not forbidden this animal, because its feet were cut off at a particular point,35Thus according to the Rambam - and his position is cited by the Shulchan Aruch (Yoreh De'ah 55:1) - if an animal's leg is severed in the top bone, it is trefe. If it is severed in the bottom bone, it is kosher, and if it is severed in the middle bone, the ruling depends on whether it was severed above the juncture of the sinews or not.
The Shulchan Aruch also cites a more stringent view - and the Rama states that it should be followed - that if the middle bone was severed, even above the juncture of the sinews, the animal is trefe. Moreover, even if it is severed at the lower joint, above the cartiledge called the irkum, the animal is trefe.
but rather because its sinews were severed36The Kessef Mishneh states that the Rambam is explaining that a severed leg causes an animal to be considered trefe, because it is in the category of chasairah. When the juncture of its sinews is lacking, it is considered trefe, because it is in the category of netulah, as the Rambam proceeds to explain. and this renders it trefe, as will be explained.37See Halachot 16-17.

הלכה טז
נְטוּלָה כֵּיצַד. שְׁלֹשָׁה אֵיבָרִים הֵן שֶׁאִם נִטְּלוּ טְרֵפָה וְאַף עַל פִּי שֶׁאֵין בָּהֶן דִּין נֶקֶב וְלֹא דִּין חֶסְרוֹן. וְאֵלּוּ הֵן. צֹמֶת הַגִּידִים. וְהַכָּבֵד. וּלְחִי הָעֶלְיוֹן:
כסף משנה
16.
What is meant by the term Netulah?38Netulah is one of the eight types of trefot mentioned in Chapter 5, Halachah 2. The term literally means "removed." There are three limbs and organs which even though they do not [cause an animal to be deemed trefe] when they are perforated or if they are lacking [when the animal is born],39I.e., there are many organs besides these three that cause an animal to be deemed lacking if they are removed. The disqualification of these other organs, however, is not included in the category of netulah, rather that of nekuvah, perforated, or chasairah, lacking, i.e., the organ's removal is the greatest perforation or lack that could be. See Chapter 6, Halachah 20. cause the animal to be deemed trefe. They are: the juncture of the sinews,40The Ra'avad notes that seemingly, the disqualification of an animal because the junction of its sinews was severed would cause it to be placed in the following category, pesukah (Chapter 9, Halachah 1). He and the Kessef Mishneh explan that since our Sages (Chullin 57a, 76a) uses the expression: "If the juncture of the sinews was removed," it should be placed in this category and not in the other. Note the Siftei Cohen 56:1 who interprets the Ra'avad slightly differently. the liver, and the upper jaw-bone.

הלכה יז
וּכְבָר בֵּאַרְנוּ שֶׁהַבְּהֵמָה שֶׁנֶּחְתַּךְ רַגְלָהּ וְכֵן הָעוֹף בִּמְקוֹם צֹמֶת הַגִּידִים לֹא נַעֲשׂוּ טְרֵפָה אֶלָּא מִפְּנֵי שֶׁנֶּחְתְּכוּ הַגִּידִין. לְפִיכָךְ אִם נֶחְתְּכוּ הַגִּידִים לְבַדָּם וְהָרֶגֶל קַיֶּמֶת טְרֵפָה שֶׁהֲרֵי נִטְּלָה צֹמֶת הַגִּידִים:
כסף משנה
17.
We already explained41Halachah 15. that when an animal or a fowl has had its legs cut off at the place of the juncture of the sinews, it is deemed trefe only because the sinews were cut.42I.e., the fact that this portion of the leg is missing is not significant. Therefore if the sinews alone were severed even though the foot remains intact, the animal is trefe, because the juncture of the sinews has been removed.

הלכה יח
נֶחְתַּךְ בִּבְהֵמָה הָאֶחָד הֶעָבֶה לְבַדּוֹ מֻתֶּרֶת. שֶׁהֲרֵי נִשְׁאֲרוּ שְׁנַיִם. נֶחְתְּכוּ הַשְּׁנַיִם הַדַּקִּין מֻתֶּרֶת שֶׁהֲרֵי הָאֶחָד הֶעָבֶה גְּדוֹל שְׁנֵיהֶן וַהֲרֵי לֹא נִטַּל כָּל הַצֹּמֶת אֶלָּא מִעוּטָהּ. נֶחְתַּךְ רֻבּוֹ שֶׁל כָּל אֶחָד מֵהֶן טְרֵפָה. וְאֵין צָרִיךְ לוֹמַר שֶׁנֶּחְתְּכוּ כֻּלָּן אוֹ נִטְּלוּ כֻּלָּן:
כסף משנה
18.
In an animal, if the thick sinew alone was severed, [the animal] is permitted, for the two [thin] ones remained. If both thin ones were severed, [the animal] is permitted, for the one thick one is larger than both of them. [In both cases,] the entire juncture was not removed, only its smaller portion.43As long as a majority - either a majority in number or the larger portion - remains intact, the animal is permitted (Chullin 76b). If the majority of each of them was severed, [the animal] is trefe. Needless to say, this applies if they were all severed or removed.

הלכה יט
וּבָעוֹף אֲפִלּוּ נֶחְתַּךְ רֻבּוֹ שֶׁל (כָּל) אֶחָד מִן הַשִּׁשָּׁה עָשָׂר טְרֵפָה:
כסף משנה
19.
With regard to a fowl, even if the majority of one of the sixteen were severed, [the animal] is trefe.44The Kessef Mishneh explains this ruling as follows. Since we are stringent with regard to a fowl and require that all sixteen be intact, we extend that stringency and disqualify it if the majority of one is impaired. For when the majority of a sinew is impaired, it is as if the entire sinew is impaired.

הלכה כ
וְעוֹף שֶׁנִּשְׁתַּבְּרוּ אֲגַפָּיו מֻתָּר כִּבְהֵמָה שֶׁנֶּחְתְּכוּ יָדֶיהָ:
כסף משנה
20.
When a fowl's wings are broken, it is permitted like an animal whose forelegs have been cut off.45As stated in Halachah 11. See Shulchan Aruch (Yoreh De'ah 53:2-3) which explains details about this situation.

הלכה כא
כָּבֵד שֶׁנִּטְּלָה כֻּלָּהּ טְרֵפָה. וְאִם נִשְׁתַּיֵּר מִמֶּנָּה כְּזַיִת בְּמָקוֹם שֶׁהִיא תְּלוּיָה בּוֹ וּכְזַיִת בִּמְקוֹם מָרָה הֲרֵי זוֹ מֻתֶּרֶת. נִדַּלְדְּלָה הַכָּבֵד וַהֲרֵי הִיא מְעֹרָה בַּטַּרְפַּשׁ שֶׁלָּהּ מֻתֶּרֶת. נִטַּל מִמֶּנָּה מָקוֹם שֶׁהִיא תְּלוּיָה בּוֹ וּמְקוֹם הַמָּרָה וְאַף עַל פִּי שֶׁהַשְּׁאָר קַיָּם כְּמוֹ שֶׁהוּא טְרֵפָה:
כסף משנה
21.
When the entire liver has been removed, [the animal] is trefe. If an olive-sized portion remains at the place from which it is suspended46I.e., near the kidneys. In his Commentary to the Mishnah (Chullin3:1) refers to it as the place attached to the blood vessels from which blood from the liver is dispersed throughout the body. Chullin 46a refers to this as "the place from which it derives its nurture." See the Siftei Cohen 41:1 and the Turei Zahav 41:1 which quote authorities that interpret this as meaning the place to which it is attached on the diaphragm. and there is an olive-sized portion at the place of the gall-bladder, it is permitted.47For these are fundamentally necessary for its functioning.
If the liver slipped from its place and it is [in disarray, as long as it is still] connected with the diaphragm, [the animal] is permitted.48Because it - and its two fundamentally necessary portions - are still intact. If the place from which it is suspended and the portion at the place of the gall-bladder were removed, it is trefe49For these two portions are of primary necessity. even if the remainder is intact as it was previously.

הלכה כב
נִשְׁאַר בָּהּ כְּזַיִת בִּמְקוֹם מָרָה וּכְזַיִת בְּמָקוֹם שֶׁהִיא תְּלוּיָה בּוֹ כְּשֵׁרָה. אֲבָל הָיָה מְפֻזָּר מְעַט בְּכָאן וּמְעַט בְּכָאן אוֹ שֶׁהָיָה מְרֻדָּד אוֹ שֶׁהָיָה אָרֹךְ כִּרְצוּעָה הֲרֵי זוֹ סָפֵק וְיֵרָאֶה לִי שֶׁהִיא אֲסוּרָה:
כסף משנה
22.
If there remained an olive-sized portion at the place of the gall-bladder and an olive-sized portion at the place from which it was suspended, [the animal] is kosher. If, however, the portions of the liver which remain intact were scattered, some here and some there, flattened, or elongated like a strap, there is a doubt concerning its status. It appears to me that it is forbidden.50Chullin 46a raises questions regarding these situations and does not resolve them. The commentaries question why the Rambam rules definitively that the animal is unacceptable. The Kessef Mishneh explains that this applies even if there is one olive-sized portion that is entirely intact.

הלכה כג
לְחִי הָעֶלְיוֹן שֶׁנִּטַּל טְרֵפָה. אֲבָל אִם נִטַּל הַתַּחְתּוֹן כְּגוֹן שֶׁנִּגְמַם עַד מְקוֹם הַסִּימָנִין וְלֹא נֶעֶקְרוּ הֲרֵי זוֹ מֻתֶּרֶת:
כסף משנה
23.
When the upper jaw-bone is removed, [the animal] is trefe.51The Tur (Yoreh De'ah 33) objects to the Rambam's ruling, stating: "I am amazed at his prohibition [of the animal] when the upper jaw is removed since this is not explicitly stated. Are we to add to the trefot?"
To explain: Chullin 54a states that if the lower jaw is removed, the animal is permitted. The Rambam deduces that the implication is that if the upper jaw is removed, the animal is trefe. The Tur claims that this deduction is not explicitly stated and hence, we have no right to make this deduction on our own. The sages of Provence wrote to the Rambam, voicing similar objections and he replied to them, explaining that the upper jaw is necessary for an animal's breathing. The Shulchan Aruch (Yoreh De'ah 33:2) states that it is proper to show respect for the Rambam's ruling.
Based on the gloss of the Rogatchover Gaon, it is possible to explain why this defect is not mentioned by the Sages of the Talmud. This defect is not in and of itself a direct cause for an animal's death, it is only a side factor that will lead to its death. Hence our Sages did not mention it, for they mentioned only those factors whice are direct causes (Yayin Malchut).
If, however, the lower jaw-bone is removed,52When quoting this ruling, the Shulchan Aruch (Yoreh De'ah 33:1) adds that the animal must be able to continue to survive by being force-fed. i.e., it was cut away until the place of the gullet and the windpipe, but they were not uprooted [from their connection to the throat, the animal] is permitted.

הלכה כד
כָּל אֵיבָר שֶׁנֶּאֱמַר בּוֹ שֶׁאִם הָיָה חָסֵר טְרֵפָה כָּךְ אִם נִטַּל טְרֵפָה. אֲבָל אֵיבָר שֶׁנֶּאֱמַר בּוֹ אִם נִטַּל טְרֵפָה אֵינָהּ נֶאֱסֶרֶת אֶלָּא אִם נֶחְתַּךְ אוֹתוֹ אֵיבָר. אֲבָל אִם נִבְרֵאת חֲסֵרָה אוֹתוֹ אֵיבָר הֲרֵי זוֹ מֻתֶּרֶת. שֶׁאִם לֹא תֹּאמַר כֵּן נִמְצֵאת הַחֲסֵרָה וְהַנְּטוּלָה אַחַת. וְכָל אֵיבָר שֶׁנֶּאֱמַר בּוֹ שֶׁאִם נִטַּל מֻתֶּרֶת קַל וָחֹמֶר אִם חָסֵר מִתְּחִלַּת בְּרִיָּתָהּ וְלֹא נִבְרָא שֶׁהִיא מֻתֶּרֶת:
כסף משנה
24.
Whenever it is said that an animal is trefe if a limb or organ is lacking,53I.e., the lungs and the hindlegs as stated in Halachah 1. so, too, it is trefe if that organ is removed.54As mentioned above (Chapter 6, Halachah 20), all the organs which render an animal trefe if they are perforated, also render it trefe when they are lacking or removed. Nevertheless, the Rambam places them in the category of nekuvah for that is the most inclusive classification. If, however, it is said that an animal is trefe if an organ is removed, [the animal] is not forbidden unless that organ was cut off. If, however, the animal was created lacking that organ, it is permitted. For if not, the categories of chasairah and netulah would be identical.55And our Sages listed them as separate categories, as stated in Chapter 5, Halachah 2.
The Rashba (as quoted by the Kessef Mishneh, Chapter 6, Halachah 20) differs and maintains that an animal is also trefe if it is lacking a liver from the beginning of its existence. Why then did our Sages mention chasairah and netulah as two separate categories? Because if they were not listed so, one might argue that an animal is trefe only when an organ is removed and not when it was lacking from the beginning of the animal's existence or vice versa. The Tur follows the Rashba's view. The Shulchan Aruch (Yoreh De'ah 50:72 quotes both opinions, but appears to favor the Rashba's view. The Rama states that we may rely on the Rambam when a significant loss is involved.
Whenever it is said that [an animal] is permitted if a limb is removed, it is certainly permitted56For the ruling is more lenient if at the outset, it was not created with this organ, as above. if this organ was lacking from the beginning of the animal's existence and was never created.

הלכה כה
בְּהֵמָה שֶׁנִּטְּלָה הָאֵם שֶׁלָּהּ וְהוּא בֵּית הָרֶחֶם אוֹ שֶׁנִּטְּלוּ הַכְּלָיוֹת הֲרֵי זוֹ מֻתֶּרֶת. לְפִיכָךְ אִם נִבְרֵאת בְּכוּלְיָא אַחַת אוֹ בְּשָׁלֹשׁ כְּלָיוֹת מֻתֶּרֶת. וְכֵן אִם נִקְּבָה הַכּוּלְיָא מֻתֶּרֶת:
כסף משנה
25.
When the uterus of an animal, i.e., its womb, was removed or its kidneys were removed,57I.e., even if both kidneys were removed. Even though according to medical knowledge, there is no way such an animal can live, our Sages did not deem this condition trefe. See Chapter 10, Halachah 12. it is permitted. Therefore if it was created with only one kidney or with three kidneys58For we follow the principle that any extra organ is considered as if it was removed. it is permitted.59It is, however, considered a blemish and the animal may not be offered as a sacrifice (Hilchot Issurei HaMizbe'ach 2:11). Similarly, it is permitted if a kidney was perforated.

הלכה כו
אַף עַל פִּי שֶׁהַכּוּלְיָא שֶׁנִּטְּלָה אוֹ חֲסֵרָה מֻתֶּרֶת אִם נִמְצֵאת קְטַנָּה בְּיוֹתֵר. וְהַקְּטַנָּה בְּדָקָה עַד כְּפוֹל וּבְגַסָּה עַד כְּעֵנָב. טְרֵפָה. וְכֵן אִם לָקְתָה הַכּוּלְיָא וְהוּא שֶׁיֵּעָשֶׂה בְּשָׂרָהּ כִּבְשַׂר הַמֵּת שֶׁהִבְאִישׁ אַחַר יָמִים שֶׁאִם תֶּאֱחֹז בְּמִקְצָתוֹ יִתְמַסְמֵס וְיִפּל וְהִגִּיעַ חלִי זֶה עַד הַלָּבָן שֶׁבְּתוֹךְ הַכּוּלְיָא הֲרֵי זוֹ טְרֵפָה. וְכֵן אִם נִמְצֵאת בַּכּוּלְיָא לֵחָה אַף עַל פִּי שֶׁאֵינָהּ סְרוּחָה אוֹ שֶׁנִּמְצָא בָּהּ מַיִם עֲכוּרִין אוֹ סְרוּחִים הֲרֵי זוֹ טְרֵפָה. אֲבָל אִם נִמְצְאוּ בָּהּ מַיִם זַכִּים הֲרֵי זוֹ מֻתֶּרֶת:
כסף משנה
26.
Although [an animal] is permitted despite the fact that a kidney was removed or it was created without it, if its kidney is extremely undersized, it is trefe.60In his Kessef Mishneh, Rav Yosef Caro states that many Rishonim disqualify an animal only when its kidneys shrank because of illness. If, however, it was born with an undersized kidney, it is acceptable. And in his Shulchan Aruch (Yoreh De'ah 44:5), he accepts this ruling as law. For a small animal, this means the size of a bean, for a large one, the size of a grape.61The Turei Zahav 44:12 and the Siftei Cohen 44:13 quote authorities who explain that the grapes of Eretz Yisrael were very large during the Talmudic period. At that time, a grape was significantly larger than a bean. Similarly, [an animal could be deemed trefe] if a kidney became afflicted, i.e., its flesh became like the flesh of a dead [animal] that decayed after several days, [degenerating] to the extent that were one to take hold of a portion of it, it would decompose and fall apart. If this condition reached the white portion62The white fat from the loins enters the kidneys, because the different sinews are all interwoven there, causing a split to appear within the kidney. This is located in the midst of the kidney (Rashi, Rabenu Nissim, Chullin 55b). in the kidney, the animal is trefe. Similarly, if moisture - even if it is not putrid - is found in the kidney or murky or putrid fluid is found there, it is trefe. If, however, clear water is found there,63Even if it reached the white portion [Shulchan Aruch (Yoreh De'ah 44:2)]. [the animal] is permitted.

קדושה הלכות שחיטה פרק ח
Kedushah Shechitah Chapter 8