Two questions:
I am unclear whether the foods listed as causing tumah, actually cause ziva or keri, two distinct substances:
On the one hand, we are bodek a zov to find out whether his ziva was caused by overeating these foods. That implies that they cause ziva, not keri.
However, Rashi (D"H liy'dei chimum) says that these foods cause keri because they are marbeh zera.
Furthermore, if they cause ziva, what would be the problem of the kohen gadol eating these foods?--Ziva caused by excessive food is tahor!
The Mishna 18a talks about the procedure on erev Yom Kippur. The Mishna 18b continues, that the kohen gadol was handed over to Beis Avtinus, to learn "chafina". This presumably was also on erev Yom Kippur. However the Gemara says 19a the kohen gadol's shedule the entire seven days prior to Yom Kippur (see Rashi D"H umeysech raglov) included a daily visit to Beis Avtinus, to learn "chafina". So when exactly was the hand-off of the ziknei kehuna to Beis Avtinus?
Thank you.
Joseph Young, Michigan
1. The common problem they were worried about regarding the Kohen Gadol was Keri, which is why these foods were not allowed from Erev Yom Kippur. However, they can cause Zivah as well. It happens to be that a Zav should not eat these foods while counting seven clean days, as despite the fact that it does not cause a person to become a Zav if he sees Zivah due to these foods, it does cause him to have to start counting his seven clean days again (see Meiri here and Nidah 37a).
2. This indeed seems to be the subject of an argument. As you noted, Rashi seemingly holds that this applied all seven days. The simple explanation of the Mishnah seems to be that this only refers to Erev Yom Kippur, and this is indeed the explanation given the Tifers Yisrael and Hon Ashir in their commentary on the Mishnayos.
All the best,
Yaakov Montrose