Gemara

(Rav Nachman): If a pregnant woman sat on the Mashber (birthing stool) and died on Shabbos, we bring a knife, cut her open and remove the fetus.

Question: This is obvious. (Even if the fetus is dead,) we merely cut dead flesh!

Answer (Rabah): He teaches that we may bring a knife through a Reshus ha'Rabim.

Chulin 11b (Rav Kahana) Question: Why may we execute a murderer? Perhaps the victim was a Treifah, and the murderer is exempt!

Answer: We rely on the majority of people, who are healthy (not Treifah).

Suggestion: Perhaps really, we must check that the victim was not Treifah!

Rejection: That would be a disgrace to the corpse!

Question: Perhaps we do so, since this may save the life of the murderer!

Rishonim

Rambam (Hilchos Shabbos 2:15): If a pregnant woman sat on the Mashber and died on Shabbos, we bring a knife, cut her open and remove the fetus. Perhaps it is alive.

Question: When Reuven died, he commanded that they bury him in his ancestors' burial site. There was an Ones that day, and they could not do so. They buried him temporarily where he died. Now, they want to take him to his fathers' burial site. Due to the stench of the rotting corpse, they cannot do so until the flesh is consumed. May they put lime on the entire body to speed the process, or is this disgrace to the Mes, or pain? The Gemara says that worms for the Mes are like a needle to live flesh. Also, is it permitted to re-inter (move the body), like he commanded?

Answer (Rashba 369): It is permitted. This is not a disgrace to the Mes. The Mes' flesh does not feel a knife, and all the more so lime. Embalmers cut and remove the intestines, and it is not painful or disgraceful. The Isur to re-inter is when it is for mere honor, without a real need. This is a need. A person wants to be buried near his fathers - "Kivru Osi El Avosai." The Yerushalmi permits this even from an honorable grave to a lowly grave. We always permit when he was initially buried with intent to re-inter. A case occurred in which one was buried in the neighborhood, because it was a Nochri holiday and they could not bury him in the cemetery. Afterwards, they moved him to the cemetery. All the more so it is permitted here, for he commanded and he was buried with this intent. It is a Mitzvah for his children to fulfill his words.

Poskim

Shulchan Aruch (OC 330:5): If a pregnant woman sat on the Mashber and died on Shabbos, we bring a knife even through Reshus ha'Rabim, cut her open and remove the fetus. Perhaps it is alive.

Rema: Nowadays we do not do so even during the week, for we are not experts to know exactly when is death, that it is still possible for the child to live a short while (until we cut her open).

Mishnah Berurah (17): The only Chidush is the Heter to bring the knife. It is no Chidush to cut her stomach if she died. This is like cutting meat!

Rema (YD 363:2): If a man commanded to be taken elsewhere for burial, they may put lime on the body to speed the decay and take him to where he commanded.

Noda bi'Yehudah (2 YD 210): A case occurred in which a man had a kidney stone. The doctors cut like they normally do, but could not heal him and he died. May they cut the body in order to understand this problem better, so if it occurs again, they will know what must be cut? If they can cut less, this decreases the danger. Is it forbidden due to disgrace to the Mes, or permitted because it can lead to saving lives in the future? Rabanan argued about this. The lenient opinion learned from embalming, which the Torah records regarding Yakov and Yosef and Yisrael kings. Even though this was for their honor, here also it honors the Mes to help others. The Rema brings the Rashba's Heter to put lime on the body to speed the decay. This is for a temporary need, to take him to where he commanded. All the more so it is permitted here, before burial! The lenient opinion brought a proof from Chulin 11b. In order to save the murderer's life, we could disgrace the Mes. That Gemara is astounding. It suggested that we (do not follow the majority), and we disgrace the Mes in order to kill the murderer! Rather, it means that if we may not disgrace the Mes, you must say that we follow the majority. It is better to say that we may disgrace the Mes, due to "v'Hitzilu ha'Edah" to try to save the murderer. Also, if the only way to kill the murderer is through checking, this is the Mes' honor.

Rebuttal (Binyan Tziyon 170): There is no proof from Chulin. If two Mitzvos oppose each other, we are passive. We needed a proof that Aseh Docheh Lo Sa'aseh. If Piku'ach Nefesh opposes disgracing a Mes, without a proof we are passive. The case in Chulin is different. There we suggested checking to save not only the murderer, rather, also the Beis Din and witnesses from bloodshed! This is why it said 'due to Ivud (making perish a) Neshamah', as opposed to 'Piku'ach Nefesh.' Even though even Safek Piku'ach Nefesh overrides everything (except for three Mitzvos, for which we have sources), Rashi (Bava Kama 60b dh v'Yatzilah) says that one may not save oneself with another's money. (Tosfos Rosh and the Rosh explain differently.) All the more so one may not disgrace to save oneself, since one's honor is dearer to him than his money.

Noda bi'Yehudah: The questioner said all this. I say that a Safek Piku'ach Nefesh overrides even Shabbos, and all the more so disgrace to a Mes. However, here there is no Choleh (sick person) in front of us, just they want to learn in case there will be more Cholim. Surely this does not override any Torah Isur or even a mid'Rabanan. If not, all cures would be permitted on Shabbos, lest a Choleh will come! We do not distinguish between likely and unlikely possibilities. Even Nochrim dissect for the sake of experiment only people killed by the king, or one who consented to this.

Chasam Sofer (YD 336): Seemingly, it is forbidden because one may not benefit from a Yisrael's corpse! This is an Isur Torah. We learn from a Mes the Isur of what is offered to idolatry and Yayin Nesech! One may not feed it to a Hefker dog. All the more so one may not sell or give it to a Nochri! Even if one said that he permits this after his death, it is forbidden. If he is not concerned for his own honor, he must be concerned for his Creator's!

Chazon Ish (Ohalos 22:32 DH b'Pischei): Pischei Teshuvah brings from the Noda bi'Yehudah and Chasam Sofer that if a Choleh were in front of us, we may disgrace it for the sake of Piku'ach Nefesh. Really, it does not depend on whether or not there is a Choleh here, rather, whether it is common. At a time when we are Masri'a (cry out in prayer, or blow the Shofar) due to a contagious disease, this is like enemies besieging a border city. In peacetime, this is not considered Piku'ach Nefesh, even though sometimes it is needed. We may not make weapons on Shabbos in peacetime. If not, all Mitzvos are Batel. Things that might occur, without any basis in the present, are not called Safek Piku'ach Nefesh. We cannot predict the future. Things that we think might happen do not always happen. What we think will save, sometimes hurts. Even for the Rabim, perhaps we permit only to avoid damage to the Rabim. The Chasam Sofer says that a Mes is Asur b'Hana'ah. If so, it is forbidden even for one who separated from the Tzibur, for whom there is no Isur to disgrace him. The Gra concluded that one may benefit from a dead Nochri.

Suggestion: We learn from Erchin that one may disgrace a Mes (cut the mother) for the sake of Piku'ach Nefesh.

Rebuttal (Binyan Tziyon 171): Disgrace is only making the Mes lowly in the eyes of those who see it, i.e. what is disgraceful even for living people. Often babies are born Yotzei Dofen (through Caesarian section)! To dissect the intestines is disgraceful. One who is having a difficult birth realizes that if she dies, perhaps they will cut her to save the child. She pardons her disgrace. Even if you will say that opening her stomach is disgraceful, and she does not pardon it, just like we may kill the fetus to save her (before it is born), after she dies, (one may cut her to save the baby.) One who kills the baby is liable, for it is as if it is (born and) in a box (Tosfos Nidah 44b DH Ihu, Ramban, Magen Avraham 330:15). If we can disgrace for the sake of money, all the more so we may disgrace a Mes that is locking up and endangering a person! We cannot learn to permit disgrace to a Mes that is not threatening the living person.

Suggestion: We must say that Piku'ach Nefesh overrides disgrace to a Mes. If not, a Kal va'Chomer would teach that burial of a Mes Mitzvah overrides Shabbos! (I.e. if disgrace to a Mes overrides Piku'ach Nefesh, then surely it overrides Shabbos, for Piku'ach Nefesh overrides Shabbos - PF.)

Rejection (Binyan Tziyon): This assumes that the Isur to disgrace a Mes is due to honor for the Mes. This is wrong. Rather, it is due to the Isur to steal the Mes' honor. This is greater than a living person's money. One who does not bury a Mes does not steal, just he is not concerned for its honor. Surely honor to a Mes does not override Piku'ach Nefesh. Would anyone think that if a person chanced upon burial of a Mes Mitzvah and Piku'ach Nefesh, that it is better to bury the Mes than to save the person?! I said only that one may not disgrace a Mes and steal its honor in order to save a person. Even if the Noda bi'Yehudah and Chasam Sofer did not rule like this, I say that had they heard my arguments and disagreed, I would concede to their opinion. However, they did not address my proof, that one may not steal for Piku'ach Nefesh.

Igros Moshe (YD 2:151): The Noda bi'Yehudah concluded that we do not override any Isur in order to learn about curing a sickness if there is no Choleh in front of us. I add that even if this concern would override Isurim, it would not override the Isur to dissect a Mes. There is no obligation to learn (Refu'ah). The Chiyuv is only to save people whom he is able to save. If one is already a doctor, he is obligated to cure Cholim. If he can swim, he must swim to save one who (he sees) drowning. One need not learn how to swim or heal in case these situations will occur, just like one need not earn much money in order to give Tzedakah and save people with the money. The Chiyuv is based only on what he can do now. People who just learned Torah like R. Shimon and his colleagues engaged in work only to earn the essentials to live. This was considered the greatest level, even though had they worked a lot they could have become rich and saved many people. Even one who constantly learns is obligated to save people!

Note: From Chovos ha'Levavos (Sha'ar ha'Bitachon 4 DH u'Perush), I see no source to say that working more would have caused then to become rich!

Igros Moshe: The Noda bi'Yehudah's reason was weak. Cholim are common. Especially nowadays we can know about all the hospitals in the world if there are such Cholim, and speedily send the Refu'ah we discover! It is forbidden because there is no Chiyuv to learn Refu'ah, so one may not disgrace a Mes for this.