QUESTION: The Gemara explains that when Rebbi evaluated the "Kundis" Se'ah, he found that a bit (1/20th or 1/80th of a Beitzah for every Beitzah; see Rashi) was added to each measure. Why was that amount added to the Se'ah?

ANSWER: RASHI in Shabbos (15a, DH Chamishah v'Od) and TOSFOS here (DH Yeseirah) explain that Rebbi found that the eggs at the time of Moshe Rabeinu were slightly larger than the eggs in his days. Rebbi discovered that when we measure 207 eggs, we really are measuring slightly less than that amount of eggs would have measured in the past. Therefore, the "v'Od" was added to each egg that we measure based on present-day eggs.

Tosfos points out that this is why the additional "v'Od" measures of Rebbi are mentioned only with regard to the modern Tzipori measure. No "v'Od" measures were added to the Midbari measure, because in the Midbar proper sized eggs were used. (At the time that the Yerushalmi measure was instituted, the difference between the sizes of eggs was not yet noticeable.)

QUESTION: The Mishnah discusses various cases in which the residents of a Chatzer and the residents of a balcony above the Chatzer forgot to make an Eruv together, when they share a domain. RASHI (DH Anshei Chatzer) writes that although they did not make a joint Eruv, they did make separate Eruvin in their respective areas. Rashi also mentions that a ladder reaches from the Chatzer to the balcony, and, therefore, even if they did not make an Eruv together they will not prohibit each other from carrying in their respective domains. This is because the ladder is considered to be both a Pesach and a Mechitzah, and thus it serves to separate the two domains from each other.

Why does Rashi mention that the ladder serves as a Mechitzah? There is already a Mechitzah that separates the Chatzer from the balcony; the balcony is higher than ten Tefachim from the Chatzer and thus they are considered to be separated by a Mechitzah!

ANSWER: The RITVA explains that Rashi wants to explain the Mishnah according to all opinions. Rebbi Akiva (59b, 66b, 75a) maintains that "Regel ha'Muteres bi'Mekomah Oseres she'Lo bi'Mekomah" -- when there is one Chatzer located on the inner side of another Chatzer, and the inner Chatzer's residents' only access to the outside is via the outer Chatzer, the inner Chatzer's residents' right to walk through the outer Chatzer prohibits the residents of the outer Chatzer from carrying in their Chatzer with their own Eruv. The inner Chatzer's residents' right to walk through the outer Chatzer prohibits the residents of the outer Chatzer from carrying even when the residents of the inner Chatzer are permitted to carry in their own Chatzer (because they have an Eruv).

In the case of the Mishnah, the residents of the balcony are like the residents of the inner Chatzer who walk through an outer Chatzer. Even though they are permitted to carry in their own domain (because of their Eruv), according to Rebbi Akiva they should prohibit the residents of the Chatzer from carrying in the Chatzer, since there is no joint Eruv (and the Eruv of the outer Chatzer is ineffective because the residents of the balcony walk through the Chatzer). Therefore, Rashi says that the ladder serves as a Mechitzah to separate the two domains. It is not considered an entranceway through which the inner Chatzer's residents could prohibit the outer Chatzer's residents from carrying (see 59b).