Parts of a corpse that impart impurity include an olive-bulk of flesh, a complete limb, the majority of a corpse’s bones, and the majority of the essential bones of its skeleton, namely, its legs, spine, and ribs. All of these impart impurity via contact, carrying, and in a tent. There are also three sources of impurity that derive from a corpse, each one of which imparts impurity in two ways but does not impart impurity in a third way. And they are the following: A full ladle of dust from a corpse, and a bone the size of a barley grain, and a grave cover [golel] and a grave wall [dofek] upon which the cover rests.

A full ladle of dust imparts impurity via carrying and in a tent, but it does not impart impurity via contact, as it is impossible for one to touch all of the particles of dust simultaneously. And where among these sources of impurity is the imparting of impurity via contact applicable? It is applicable with one of those other two sources of impurity, i.e., a bone the size of a barley grain and the cover or wall of a grave.

A bone the size of a barley grain imparts impurity via carrying and contact, but it does not impart impurity in a tent. This halakha was transmitted to Moses from Sinai. And where among these sources of impurity is impurity imparted in a tent? It is with one of those other two sources of impurity.

A grave cover and a grave wall impart impurity via contact and in a tent, but they do not impart impurity via carrying. This halakha too was transmitted to Moses from Sinai. And where among these sources of impurity is impurity transmitted via carrying? It is with one of those other two sources of impurity. It may be inferred from Rabbi Shimon’s statement that a full ladle of dust imparts impurity in a tent but not via contact that he disagrees with Rabbi Yosei and holds that overlying is not the same category as touching.

§The mishna teaches: With regard to the thigh bone of an unslaughtered carcass and the thigh bone of a creeping animal, one who touches them when they are sealed remains ritually pure, because the bone itself does not impart impurity. With regard to this topic, the Sages taught in a baraita: The verse states: “One who touches the carcass thereof shall be impure until the evening” (Leviticus 11:39). The word “carcass” indicates that one who touches the carcass is impure, but one who touches a sealed thigh bone is not.

One might have thought that even one who touches a perforated thigh bone remains pure. Therefore, the verse states: “One who touches the carcass thereof [benivlatah] shall be impure,” indicating that one who touches a part of the animal through which it is possible to touch the flesh, which has the halakhic status of an unslaughtered carcass [neveila], is impure, but one who touches a part of the animal through which it is impossible to touch the flesh remains pure. Therefore, one who touches a protective layer such as the outside of a sealed thigh bone does not become impure, as it is impossible to touch the marrow.

Rabbi Zeira said to Abaye: If that is so, that one who touches the protective layer of a carcass via which it is impossible to touch the flesh of the carcass itself does not become impure, an animal still in its hide should not impart impurity, as one can touch the hide, which constitutes a protective layer, but not the flesh. Abaye answered: Go out and see how many orifices there are in the body of an animal via which one can touch the flesh, e.g., the eyes, the nostrils, and the mouth.

Similarly, Rav Pappa said to Rava: If that is so, that one who touches the protective layer of a carcass via which it is impossible to touch the flesh of the carcass itself does not become impure, the kidney of a carcass that is completely covered in its fat should not impart impurity via contact. Rava answered: Come and see how many sinews emerge from the kidney that one is able to touch.

§The mishna taught that the halakha distinguishes between a sealed and a perforated thigh bone of a carcass or a creeping animal. With regard to this topic, Rav Oshaya raises a dilemma: What is the halakha if one intended to perforate the thigh bone but did not yet perforate it? This is the dilemma: Is a thigh bone lacking perforation considered to be lacking the necessary action for it to impart impurity, and it therefore retains its status as a sealed thigh bone, or not?

Rabbi Oshaya then resolves the dilemma: A thigh bone lacking perforation is not considered to be lacking the necessary action for it to impart impurity. If one intends to perforate it, it imparts impurity immediately.

MISHNA: The egg of a creeping animal in which tissue of an embryo developed and one who comes into contact with the egg are ritually pure, as the impure creeping animal is hermetically sealed. But if one perforated the egg with a hole of any size, one who comes in contact with the egg is ritually impure. In the case of a mouse that grows from the ground and is half-flesh half-earth, one who touches the half that is flesh is impure; one who touches the half that is earth is pure. Rabbi Yehuda says: Even one who touches the half that is earth where it is adjacent to the flesh is ritually impure.

GEMARA: The mishna states that in the case of an egg of a creeping animal in which tissue of an embryo developed, if it is perforated then one who touches it is ritually impure. With regard to this matter the Sages taught in a baraita: The verse states: “These are the impure ones to you among all that creep; whoever touches them when they are dead shall be impure until the evening” (Leviticus 11:31). The term “the impure ones” is interpreted as including the egg of a creeping animal and the thigh bone of a creeping animal in the category of sources of impurity.

One might have thought that even an egg in which tissue of an embryo has not developed imparts impurity. Therefore, the verse states: “That creep,” indicating that just as a creeping animal has developed tissue, so too only the egg of a creeping animal in which tissue of an embryo has developed imparts impurity.

One might have thought that in the case of an egg in which tissue of an embryo has developed, it imparts impurity even if it was not perforated. Therefore, the verse states: “Whoever touches them when they are dead shall be impure,” indicating that when it is possible to touch the flesh, contact renders one impure; but when it is impossible to touch the flesh, one remains pure.

And how large must its perforation be to render one touching the egg or thigh bone impure? Its width must be the size of a strand of hair, as it is possible for one to touch the inside of an egg or thigh bone with a strand of his hair.

§The mishna teaches: In the case of a mouse that grows from the ground and is half-flesh half-earth, one who touches the half that is flesh is impure. Rabbi Yehoshua ben Levi says in this regard: One becomes impure in such a case only if the flesh of the mouse has developed along the entire length of the mouse, from head to foot. Some teach the statement of Rabbi Yehoshua ben Levi with regard to the latter clause of the mishna: Rabbi Yehuda says: Even one who touches the half that is earth where it is adjacent to the flesh is ritually impure. Rabbi Yehoshua ben Levi says: One becomes impure in such a case only if the flesh of the mouse has developed along the entire length of the mouse.

The one who teaches the statement of Rabbi Yehoshua ben Levi with regard to the first clause of the mishna, all the more so he teaches this same halakha with regard to the latter clause of the mishna. But the one who teaches the statement of Rabbi Yehoshua ben Levi with regard to the latter clause of the mishna holds that it applies only to that clause, with regard to one who touches the half that is earth where it is adjacent to the flesh according to Rabbi Yehuda. But according to the opinion of the first tanna, stated in the first clause of the mishna, even if the flesh of the mouse has not developed along the entire length of the mouse, one who touches the half of the mouse that is flesh is impure.

§The Sages taught in a baraita concerning the following verse: “And these are they which are impure to you among the creeping animals that creep upon the earth: The weasel, and the mouse, and the great lizard after its kinds” (Leviticus 11:29). Since “mouse” is stated among the creeping animals that impart impurity, I would derive that even a sea mouse, i.e., a sea creature that has an appearance similar to a mouse, imparts impurity because its name is also mouse. But ostensibly, the opposite conclusion could be derived through logical inference: The verse deems a weasel impure and deems a mouse impure. Therefore, just as a weasel is a species that grows on land, so too the mouse to which the verse is referring is a species that grows on land; a sea mouse does not impart impurity.

Or, perhaps go this way: The verse deems a weasel impure and deems a mouse impure; accordingly, just as “weasel” is referring to any animal whose name is weasel, so too, “mouse” is referring to any animal whose name is mouse, even a sea mouse, as its name is also mouse. Therefore, the verse states: “Upon the earth,” indicating that a land mouse imparts impurity, but a sea mouse does not.

If this halakha is derived only from the phrase “upon the earth,” one might have thought that the verse means that any mouse, whether a land mouse or a sea mouse, imparts impurity when it is upon the earth, but if it descended to the sea it does not impart impurity.