1) "ASUVEI YENUKA"
OPINIONS: Rav Nachman and Rav Sheshes argue whether "Asuvei Yenuka" is permitted on Shabbos or not. Rav Nachman attempts to prove that it is forbidden from the Mishnah (147a) that states that it is forbidden to cause Apiktevizin (vomiting) on Shabbos. Rav Sheshes attempts to prove that it is permissible from the Mishnah here (122b) that states that one may use a needle to remove a splinter on Shabbos.
What is "Asuvei Yenuka," and how is it comparable to Apiktevizin and removal of a splinter?
(a) RASHI explains that Asuvei Yenuka refers to manipulating the bones and joints of a baby in order to straighten them into their proper positions. It is comparable to Apiktevizin because it is a corrective procedure which involves manipulating the body. In this respect it is also similar to removing a splinter. (Rashi later (147b), however, says that Apiktevizin has medicinal properties, and it is not merely a corrective procedure; see Rebbi Akiva Eiger in Gilyon Hashas.)
According to Rashi, it is not clear why the Gemara states at the end of the Sugya that a splinter is not comparable to Asuvei Yenuka because it is "Lo Pakid." It should have said that a splinter is not part of the person's body, while Asuvei Yenuka involves adjusting parts of the body!
(b) RABEINU CHANANEL, the BA'AL HA'ME'OR, and the ARUCH explain that Asuvei Yenuka refers to a disorder in which a certain cartilage or bone in the upper throat of the child descends into the lower part of the throat (either the esophagus or trachea). A nurse puts her finger down his throat in order to bring the bone back into its proper position. Since the treatment can cause vomiting, the Gemara compares it to Apiktevizin.
This explanation, too, is difficult to understand. How is this treatment comparable to the removal of a splinter? Furthermore, the comparison to Apiktevizin is not clear, because the nurse has no intention to cause the child to vomit, and thus her act is a Davar she'Eino Miskaven with regard to Apiktevizin.
The RITVA answers that, normally, the nurse who performs the procedure of Asuvei Yenuka causes the child to vomit and spit up blood (which is forbidden because of Netilas Neshamah). Therefore, such an act falls into the category of Pesik Reshei (something which is definitely going to occur and thus is forbidden even if one had no intention for it to occur). Accordingly, the Gemara's question is whether the Rabanan permitted an act of Eino Miskaven which nearly always causes a Melachah to be done, for the sake of healing on Shabbos. In this respect it is comparable to the removal of a splinter, which also usually causes blood to flow and is therefore a Pesik Reshei. (Rav Sheshes, who permits the act to be done, apparently does not consider it to be a Pesik Reishei, since it is possible that there will be no bleeding. Nevertheless, he does not permit such an act for non-therapeutic purposes, since it is very close to a Pesik Reishei. -M. KORNFELD)
(c) The Rishonim cite RABEINU TAM who says that the question is whether one may open a closed duct in order to take something out of it. Is such an act considered healing or not? According to Rabeinu Tam, the case of the bone that became displaced, the case of causing one to vomit, and the case of the removal of a splinter are all cases that involve opening a closed duct for the sake of healing. The Gemara answers that the splinter is "Lo Pakid" -- it is not the same as Asuvei Yenuka because it is merely deposited underneath the skin. It does not block any natural path that will be used as a duct of some sort. The throat, in contrast, is a duct that needs to be opened in order to allow for the passage of air and food.
2) THE HISTORICAL DEVELOPMENT OF THE PROHIBITION OF "MUKTZAH"
The Gemara relates that the prohibition of Muktzah began in the times of Nechemyah, who made an enactment (with a few exceptions) that no utensils may be handled on Shabbos. When he saw that people were desecrating Shabbos by bringing piles of wheat from the fields into the city, he made a decree that prohibited any utensil to be carried.
The Rishonim record a number of different reasons for the decree of Muktzah. Different types of Muktzah may be related to the different reasons for the decree.
(a) The RA'AVAD (Hilchos Shabbos 24:12) says that reason for the decree of Muktzah is to prevent people from carrying from Reshus ha'Yachid to Reshus ha'Rabim on Shabbos (like the purpose of the original decree of Nechemyah). This reason is supported by the Gemara later (124b).
(b) The RAMBAM does not mention this reason, but he lists three other reasons for the decree of Muktzah. First, the decree of Muktzah is intended to prevent a person from making his Shabbos into a regular weekday by carrying all of his things around all day. Second, conversely, a person who does not work during the week needs some way to designate the day of Shabbos as different from the weekdays. It is the prohibition of Muktzah that distinguishes Shabbos from the weekdays for such a person. Third, the Rabanan prohibited handling a utensil used primarily for a labor which is forbidden on Shabbos (Kli she'Melachto l'Isur), lest one inadvertently use it for its purpose and do a Melachah on Shabbos.
(c) The Gemara in Beitzah (2b) and Eruvin (38b) gives another source for the prohibition of Muktzah: "Hachanah d'Rabah." Rabah derives from a verse in the Torah that one is required to prepare things prior to Shabbos for use on Shabbos. If one did not prepare them prior to Shabbos, they are forbidden to be used on Shabbos. According to this source, it seems that the prohibition of Muktzah is mid'Oraisa. Does this conflict with our Gemara which states that Muktzah is only a decree mid'Rabanan from the time of Nechemyah?
The CHASAM SOFER (introduction to Mahadura Tinyana on Beitzah) explains that there are different parts to the decree of Muktzah. We find that the Gemara later in Shabbos (128a) differentiates between eating Muktzah and handling or moving it. Rabah's source for the prohibition of Muktzah, which implies that Muktzah is an Isur mid'Oraisa, refers to an Isur to eat (or consume, such as in the case of firewood) items which were not prepared before Shabbos. There is no source from that verse to prohibit handling Muktzah; that prohibition comes from the decree of Nechemyah.