The Mishnah teaches that one who finds an animal within a certain distance from Yerushalayim must assume that it was designated as a Korban. If it is a male animal, it is offered as an Olah, and if it is a female animal, it is offered as a Shelamim. The Gemara questions why we assume that a lost male animal is an Olah.
The text of the Gemara, however, is unclear, and the VILNA GA'ON makes extensive changes in the Girsa. To understand the Sugya here, one must learn the complementary Sugya in Kidushin (55a) which discusses this Mishnah and deals with many of the issues discussed by the Gemara here.
The Vilna Ga'on's changes are based on the Gemara in Kidushin. After one analyzes his approach, one will notice that the Sugya here can be understood the same way that the Vilna Ga'on understands it, but without the changes in the Girsa that he makes.
(Disciples of the Vilna Ga'on write in numerous places that their teacher taught them Sugyos in the Yerushalmi with the original Girsa, but explained those Sugyos in such a way that the explanation matched his suggested Girsa changes (see, for example, BNEI MOSHE). This may be an important rule to keep in mind when one considers how the Vilna Ga'on made such numerous and extensive emendations in the conventional text of the Mishnah and Yerushalmi. -M. Kornfeld.)
The flow of the Gemara may be divided into five stages:
1. The Mishnah asserts that a male animal is assumed to be an Olah. The Gemara questions this assertion. A male animal can also be a Shelamim, and thus perhaps this animal was designated to be offered as a Shelamim and not as an Olah. Why, then, does the Mishnah say that the animal is assumed to be an Olah? The Gemara, therefore, assumes that the Mishnah does not mean that the animal is offered as an Olah; rather, the Mishnah means that the animal is offered as both an Olah and a Shelamim.
How, though, can one animal be offered as two Korbanos? It must be that the person transfers the Kedushah of the animal onto two new animals, one of which will be offered as an Olah and the other as a Shelamim. He stipulates, "If the original animal is an Olah, then I hereby transfer its Kedushah onto the first new animal. If it is a Shelamim, then I hereby transfer its Kedushah onto the second new animal. The remaining animal that is not sanctified will be offered as a Nedavah."
This is the intention of Rebbi Hoshiyah when he says, "la'Vo b'Demeihen Shanu." He means that one does not offer the actual animal that was found, but rather he offers two other animals, one as an Olah and one as a Shelamim, that are each equal in value to the original animal.
(Of course, the finder is not obligated to do this, for it involves donating a second animal from his own funds. If he wants, he may leave the animal to graze until it becomes blemished and then redeem it. However, if he wants to avoid any doubt and bring the correct Korban with this animal, this is the preferable procedure.)
2. The Gemara questions this procedure. Nowhere else does the law permit one to redeem a perfect, unblemished animal onto another animal. Why, in this case, does the Mishnah suggest that one may redeem an unblemished animal and bring two animals, each of equal value to the first, in its place?
The Gemara in Kidushin explains that, indeed, no act of Chilul (transfer of Kedushah) is performed in this case. Rather, the original animal loses its Kedushah through Me'ilah (misuse of Kodshim, such as using it to purchase another animal). Me'ilah, like Chilul, removes the Kedushah from a sanctified object, even from an unblemished animal. (Although there is a principle that the Kedushah of Kodshei Mizbe'ach, such as Korbanos, cannot be removed, that applies only when one does not intend to remove the Kedushah. When one intends to remove the Kedushah, the Kedushah can effectively be removed.) If one has intention to remove the Kedushah from the animal, it is considered as though he does an act of Me'ilah which removes its Kedushah. However, he is able to remove the Kedushah in this manner only according to the opinion of Rebbi Meir in Kidushin (54b), who says that Me'ilah committed intentionally (b'Mezid) is able to remove the Kedushah of an object. Rebbi Yehudah argues and says that the Kedushah leaves the object only when Me'ilah is committed unintentionally (b'Shogeg).
However, this raises a new problem. Why is the person told to commit Me'ilah ("Tzei u'Me'ol b'Kodshim") in order to remove the animal's Kedushah? The act of Me'ilah is forbidden! The answer is that the case of the Mishnah refers to one who already committed Me'ilah (b'Di'eved); he is not instructed to do it (Tosfos, Kidushin 55a). Alternatively, the Mishnah means that since his purpose is to enable the animal (or its value) to be offered as a Korban, this form of Me'ilah is permitted.
However, Rebbi Yochanan rejects these two answers and says that this case is no different from a normal case of Me'ilah, which is forbidden. Since the Mishnah implies that one is permitted (l'Chatchilah) to make the animal into an Olah, Rebbi Hoshiyah's explanation must be incorrect.
3. The Gemara therefore returns to the beginning of the discussion and says that the reason one offers the male animal as an Olah (even though a male animal may also be offered as a Shelamim) is because most male animals are offered as Olos, since an Olah may be offered only from a male animal.
The Gemara was unaware of the implied question which Rebbi Hoshiyah earlier was answering, and therefore, only at this stage is it bothered by that question: how can this animal be offered as an Olah, if male animals may also be offered as Shelamim, and it is not logical to say that "most male animals are offered as Olos."
Rather, it must be that the Kedushah of the animal is transferred onto two other animals, one of which is offered as an Olah and the other as a Shelamim, exactly as Rebbi Hoshiyah had suggested. (The Gemara earlier did not know why Rebbi Hoshiyah said that one transfers the Kedushah from the original animal onto two new animals, one as an Olah and one as a Shelamim. It was not aware of the question that Rebbi Hoshiyah was addressing, until this point when it asks the question on its own.)
Now, however, the Gemara is bothered by the same question that it asked on Rebbi Hoshiyah: why is one permitted to remove the Kedushah from an unblemished animal and transfer it onto another animal? The Gemara asks, "Keitzad Hu Oseh, Motzi'in l'Chulin v'Chozer v'Oseh Osan Olos?" "What should he do -- redeem the animal and bring with its value Olos [and Shelamim]?" One is not permitted to redeem an unblemished animal!
4. The Gemara answers ("Amar Rebbi Ze'ira") that it is not true that one may never redeem an unblemished animal. We find that a Tenai Beis Din (a stipulation of the Rabanan) is able to make a Chatas into an Olah (11b), and, similarly, it can make a Shelamim (that is in doubt) into an Olah.
5. Rebbi Yosi asks one final question. "This is Mezid" -- why is one permitted to intentionally remove the Kedushah from an animal?
What is Rebbi Yosi's question? The Gemara just established that it is a Tenai Beis Din, and thus no transgression is committed when one removes the Kedushah of the animal!
It must be that Rebbi Yosi's question refers back to Rebbi Hoshiyah's statement. Rebbi Hoshiyah said that one may commit Me'ilah and remove the Kedushah from an animal. Earlier, Rebbi Yochanan asked that one should not be permitted to do such a thing l'Chatchilah. Rebbi Yosi now asks another question on Rebbi Hoshiyah. Me'ilah removes the Kedushah from an object only when it is done unintentionally, b'Shogeg (according to Rebbi Yehudah). Although it is true that Rebbi Meir maintains that Me'ilah removes the Kedushah even when it is done b'Mezid, but the Halachah follows the view of Rebbi Yehudah. Why, then, does Rebbi Hoshiyah explain the Mishnah according to the non-Halachic opinion of Rebbi Meir? That is Rebbi Yosi's question.
The Gemara answers, as it concluded earlier, that a Tenai Beis Din allows the animal to be offered as an Olah even when it was originally set aside to be offered as a Shelamim.