Perforated intestines are likely to be sealed by internal mucous, which would leave the animal kosher. The Gemara then traces Rabbi Shimon ben Gamliel's statement on this point - namely, that it would be kosher. And Rabbi Shimon's view on mourning -- that a mourner who first hears about the death late will join the count with the family that is sitting shiva if he is close enough to join them (and then continue his own count afterwards). Until the end of the discussion, when Rabbi Shimon ben Gamliel's approach is rejected, and Rabbi Shimon's is upheld. Also, the inner and outer paunch - with a lot of detail regarding what needs to be intact to be able to call the animal kosher. But the sages themselves have a lot of questions here.