Question: This is difficult. If the neck of a dog is considered something that does not become impure, even if the neck has a diameter of a Tefach it should not make a difference!

Question (cont.): Even though Rebbi Meir holds that one can view an area as carved away in order to complete an amount, the flesh here is lessening the airspace from being a Tefach (inside the neck) and this blocks the impurity from coming.

Question (cont.): If the dog is considered something that could become impure, how could Rebbi Yosi say that we look at where the impurity is located (in relation to whether it is inside or outside the house)? This indicates that if there is not a Tefach of airspace, it would not bring impurity. Why? If the dog cannot interrupt the impurity (as it itself can become impure, and therefore it cannot act as an interruption), it should be as if it is in the airspace of the house!

Answer: However, it is possible that the house will still be pure according to Rebbi Yosi. Since there is not a space of a Tefach, there is no Ohel that causes the impurity to go to the house, and the impurity stops outside.

Question: However, there is a difficulty. Even if the flesh does not interrupt the impurity, why don't the bones interrupt the impurity?

Answer: Rebbi Meir understands that we can view an area as carved away in order to complete an amount, and there is some air as bones do not close the entire whole but rather lessen it. Together with the fact that the person probably does not nullify them and will eventually take them away, the bones cannot be considered an interruption. This is as I explained in Bava Basra (19b).

Explanation: "We see" means that we see if the impurity is laying in the airspace of the doorway or not.

Implied Question: Rava could not have said that Rebbi Yosi was referring to a dog that has a neck that is a diameter of a Tefach, and that he is not arguing but rather stating the doorway is not an Ohel. Additionally (according to this possibility), "We see" would be referring to the neck of the dog. (Why didn't Rava give this explanation?)

Answer: It is not possible to say "we see" refers to the neck of the dog, as it is in front of us! Rather, it is clearly either referring to the impurity inside the dog or the airspace inside the neck.

Explanation: Rebbi Meir does not require airspace of a Tefach based on his reasoning in Shabbos (7b) that we can view an area as if it is carved away in order to complete an amount. He says this (ibid.) regarding a case where a person threw something on Shabbos that landed in a small hole.

Implied Question: This is despite the fact that when the Gemara in Eiruvin (11b) discusses a round doorway, we do not say that we view the area as carved away in order to complete an amount unless there is a space of four Tefachim before it starts to become rounded.

Answer: It is possible that this is specifically regarding Mezuzah, as the Pasuk states, "And in your doorways" and we (derive from here that we) require an important doorway (before one is obligated in Mezuzah). However, normally if there would not even be four we would say we view the area as carved out. The Gemara there requires study.

Explanation: It appears that the Gemara is discussing a case where there is not a space of a Tefach under the doorway. When the door is closed, the area under the doorway is like an Ohel of its own, but an Ohel cannot be less than a Tefach (and therefore it is not a proper Ohel regarding impurity).

Explanation (cont.): Rebbi Elazar is saying that if the mouth of the dog was inside the house it causes the house to be impure, as the impurity is deemed to leave through the mouth into the house.

Explanation (cont.): It appears that Rebbi Elazar is not referring to the same case of the dog as discussed by Rebbi Yosi. Rebbi Yosi is referring to a dog that has a neck that is a diameter of a Tefach, while Rebbi Elazar is referring to a dog that has a neck that is not the diameter of a Tefach. This is apparent from the fact that he says that if its mouth is towards the inside of the house, the house is pure. This implies that he is referring to any dog, even if it does not have a neck the diameter of a Tefach.

Explanation #1: Rashi explains that the question is, who is the Tana who said earlier that if one touches half a Kzayis and something else is over him and another half a Kzayis that he is pure? This Tana holds that they do not combine because Ohel is not touching. This shows that these are two different ways of contracting impurity.

Question: This is difficult, as even Rebbi Yosi admits there according to both Abaye and Rava (125b) that if the item is more than a Tefach away from something covering it, it is not called "touching."

Explanation #2: It appears that since the Gemara earlier asked who the Tana is who considers Ohel "touching" and it answered that this is Rebbi Yosi, this implies that there is a Tana who argues on him. The Gemara wants to know the identity of that Tana.

Explanation: Rashi explains that this is a Halachah l'Moshe mi'Sinai.

Question: It is impossible to say this, as we derive this from a Pasuk in Nazir (53b).

Observation: The only Halachah l'Moshe mi'Sinai regarding this law is that a Nazir has to shave his hair for carrying or touching such a bone, even though he did not come in contact with them through Ohel.

Question: According to the opinion earlier (72a) that a Golel and Dofek cause impurity due to a Halachah l'Moshe mi'Sinai, it is possible to say that this is part of the Halachah l'Moshe mi'Sinai. However, according to the opinion that derives this from the Pasuk, "on the face of the field," how does he know the details of this law?

Answer: It appears that this is because the Pasuk, "Anyone who will touch on the face of the field" is said in Nazir (53b) to be referring to impurity through Ohel. Therefore, it is impure through Ohel. It is also impure through contact, as the Pasuk uses the word "touch." However, we do not find any indication in the Pasuk that they should be impure due to carrying.

Observation: We used this Pasuk earlier (77b) to exclude bones and sinews.

Question: This is difficult, as how can we also use the Pasuk to exclude a closed thighbone?

Answer: However, since we do not include a Shomer unless the thighbone has a hole in it that one can touch the marrow inside the bone, this must mean that when we exclude bones in general we also exclude a thighbone that is closed.

Implied Question: This is despite the fact that a Shomer can be considered to close off the item it is guarding, just like the shell of a kernel of wheat protects it by enveloping it (see 117b). (Why can't a bone be the same way?)

Answer: The Gemara there (117b) includes such a Shomer from the Pasuk, "seed that is planted." The Gemara derives that this is how people take it out to be planted. However, regarding a bone the Pasuk has revealed that it can only be called a Shomer if one can touch the marrow inside.

Observation: Similarly, regarding Sheratzim we include later from the Pasuk, "he will be impure" that a thighbone of a Sheretz that has a hole is impure.

Implied Question: This is despite the fact that we derive later from the Pasuk, "that are impure" that we include a thighbone of a Sheretz and the egg of a Sheretz. (Which Pasuk is the actual derivation?)

Answer: The main part of the Pasuk is regarding the egg of a Sheretz. However, the thighbone is indeed derived from "he will be impure."

Implied Question: This is despite the fact that from "that are impure" we derive many other teachings. (How can we derive many teachings from one Pasuk?)

Answer: It is possible that this is derived from breaking down the word into "Tamei," Temei'im," and "ha'Temei'im." It is also possible that the word "impure" is stated many different times (and we derive one teaching from each word).

Question: Why do we need a special Pasuk to teach that such an egg is impure? It is obvious that it is considered like eating a Sheretz without requiring a Pasuk to teach us that! This is as the Gemara states earlier (64a) that if a baby Sheretz was forming in the egg and one ate it he would receive lashes due to the Pasuk, "the Sheretz that is crawling on the land." This indicates it is clearly called a Sheretz!

Answer #1: If it certainly was formed in the egg, it is indeed called a Sheretz. However, it is not called a Tzav or Achbar (specific type of Sheretz).

Answer #1 (cont.): We similarly say earlier (75a) regarding forbidden fat that it is not called the fat of an ox, sheep, or goat until the fetus comes into the "air of the world."

Answer #2: Alternatively, the Pasuk in our Gemara is the source for the Gemara earlier (64a) to say that one receives lashes if he eats it.