that there is a possibility that part of the afterbirth will emerge without part of the fetus inside, and the reason that the rabbis forbid eating the afterbirth is due to a rabbinic decree prohibiting a case where part of an afterbirth emerges from the womb and part of it remains inside, due to the possibility that one may confuse it with a case where all of the afterbirth emerges. Therefore, Ulla teaches us that, in fact, part of the afterbirth does not emerge without part of the fetus inside.
ואמר עולא אמר רבי אלעזר: בכור שנטרף בתוך שלשים יום – אין פודין אותו.
The Talmud cites another halakha taught by Ulla, citing R' Elazar: And Ulla says that R' Elazar says: With regard to a male firstborn child who was mauled by an animal within 30 days of his birth and died, one is not required to redeem him, as the requirement to do so, by paying 5 sela to a priest, applies only once the child is 30 days old (see Numbers 18:15–16).
וכן תני רמי בר חמא, מתוך שנאמר: ״פדה תפדה״, יכול אפילו נטרף בתוך שלשים יום? תלמוד לומר: ״אך״ – חלק.
And similarly, Rami bar Ḥama taught a baraita: Since it is stated: “Yet you should redeem” (Numbers 18:15), one might have thought that even if a male firstborn child was mauled by an animal within 30 days of his birth one should redeem him. Therefore, the verse states “yet you should redeem”; the addition of the word “yet” serves to differentiate and limit the requirement to redeem the firstborn male.
ואמר עולא אמר רבי אלעזר: בהמה גסה נקנית במשיכה.
The Talmud cites another halakha taught by Ulla, citing R' Elazar: And Ulla says that R' Elazar says: A large animal, such as a cow or a horse, is acquired by the buyer pulling the animal.