1) THE LIMBS OF A NIDAH
QUESTION: The Gemara says that a Nidah is not Metamei l'Evarim; her limbs do not cause other things to become Tamei. This principle is difficult to understand. If the woman is alive and she loses a limb, the limb is Metamei because of Ever Min ha'Chai (a severed limb of a living person), which has the same Tum'ah as Tum'as Mes which is Metamei b'Maga, Masa, and Ohel. Accordingly, what difference does it make if it is not Metamei because of Nidah? If, on the other hand, the limb is still attached to her, then it certainly is Metamei whatever it touches, because the limb is part of the body of a Nidah!
(a) RASHI (82b) explains that the limb is severed, and even though it is Metamei because of Tum'as Mes, Tum'as Mes is not Metamei through Even Mesama, whereas Nidah is Metamei through Even Mesama. If this limb is not Metamei because of Nidah, it will not be Metamai through Even Mesama.
(b) The RAMBAM (Hilchos Metamei Mishkav u'Moshav 8:4) says that the limb is not severed but is still attached to the woman's body. It makes a difference that it is not Metamei like a Nidah in a case where a Nidah puts her arm into a Kli Cheres (an earthenware vessel) without touching the sides. A Tamei object which enters the airspace of a Kli Cheres is Metamei the Kli Cheres. However, a Kli Cheres into which a Nidah enters becomes Tamei only when the Nidah enters a Kli Cheres with her entire body. If only her hand goes into a Kli Cheres but her body is not within the vessel's airspace, then the vessel's status of Tahor or Tamei depends on whether the limb of a Nidah is Metamei.
(c) The RA'AVAD (ibid.) explains "Einah Metam'ah l'Evarim" means that a limb of a Nidah cannot cause Tum'as Mishkav or Moshav by resting upon an object. A Nidah cannot make an object Tamei with Tum'as Mishkav u'Moshav unless most of her weight rests on it. Those who maintain that a limb of a Nidah is Metamei independently are of the opinion that a limb of a Nidah can be Metamei Mishkav or Moshav by resting upon an object even if most of the weight of the Nidah is not resting upon it.
2) A BOAT THAT BECOMES "TAMEI"
QUESTION: The Gemara gives two reasons for why a boat is not Mekabel Tum'as Mes. First, the Tana of the Mishnah says that a boat is not Mekabel Tum'ah because the verse compares it to the sea (which cannot become Tamei). Second, Chananyah, in the Beraisa, says that a boat is not a vessel which can be carried both while empty and while full (it is a "Kli she'Eino Metaltel Malei v'Reikan").
TOSFOS asks that a boat should become Tamei with Tum'as Midras, because it is made for sitting and lying upon. Tum'as Midras does not depend on the ability of the vessel to be carried both while full and empty. (That type of Tum'ah is not juxtaposed with sackcloth in the verse that teaches the conditions for Tum'as Maga (Bechoros 38a). Similarly, Tum'as Midras applies even to objects that are flat and do not have receptacles.) Since a boat should become Tamei with Tum'as Midras, it should also be able to become Tamei with Tum'as Mes, because the Gemara (84b) says that anything that is Mekabel Tum'as Midras is also Mekabel Tum'as Mes! Why, then, is a boat not Mekabel Tum'ah according to Chananyah?
(a) TOSFOS (DH Nilmedah mi'Sak) says that even though people sit on the boat, the main purpose of a boat is to carry loads. A person on the boat can be told to leave in order to make room for loads. Since Tum'as Midras applies only to objects that are designated for people sit upon, it does not apply to a boat.
(b) The RAMBAN explains that people sleep on beds or sit on chairs on the boat. The boat itself, though, is like the ground, upon which people do not sleep without a covering of some sort.
(c) The RE'AH (cited by the Chidushei ha'Ran here and on 44b) says that the only time the juxtaposition to sackcloth is not made is with regard to a wooden vessel which has no receptacle (Peshutei Kli Etz). Even though it has no receptacle, a vessel stills becomes Tamei with Tum'as Midras. However, with regard to all other conditions the juxtaposition is made, and thus the conditions taught for sackcloth apply also to Tum'as Midras. (For example, the utensil must be Metaltel Malei v'Reikan in order to be Mekabel Tum'as Midras.) Anything that is not Metaltel Malei v'Rekan is not Mekabel any Tum'ah at all, neither Tum'as Midras not Tum'as Mes. (The RAMBAN here also mentions this idea, but he remains in doubt whether it is correct.)
(d) RAV MOSHE SHAPIRO shlit'a explains that the RAMBAM seems to have a different approach to this question. The Mishnah in Ohalos (8:1) teaches that a Kli that is held above a Mes does not prevent Tum'ah from spreading above it, even if the Kli is made of stone (which is not Mekabel Tum'ah itself). The Rambam (Hilchos Tum'as Mes 13:3) writes that if the stone Kli is so large ("ha'Ba b'Midah") that it cannot be carried, it does stop Tum'ah from spreading above it. What is the difference between a small stone or a large stone? If a small stone Kli does not stop Tum'ah from spreading above it even though it itself is not Mekabel Tum'ah, why should a large stone Kli stop Tum'ah from spreading above it? Apparently, the Rambam maintains that when it is so large, it is no longer called a Kli, but an Ohel, and therefore it is able to stop Tum'ah from spreading above it. Similarly, the RASH in Yadayim says that although a person may use a stone Kli for Netilas Yadayim (even though it is not Mekabel Tum'ah), one may not use a very large Kli (ha'Ba b'Midah). What is the difference between the two, if they are both Tahor? It must be that a large stone Kli is not considered a Kli at all, but an Ohel. Consequently, its Taharah has nothing to do with being compared to sackcloth. (Support for this can be drawn from the Gemara earlier, 35a.)
Therefore, in the case of the Gemara here, the Rambam learns that the boat is not Mekabel even Tum'as Midras, because it is not a Kli at all. (The RITVA (44b) mentions such an opinion and rejects it.)