Gemara

13a (Mishnah - R. Shimon): One who eats any amount of Tevel is lashed;

Chachamim say, he is lashed for a k'Zayis (the volume of an olive).

R. Shimon: Don't you agree that one is liable for eating a (full) ant of any size?

Chachamim: That is because it is a Briyah (a full creation).

R. Shimon: Also a wheat kernel is a Briyah!

17a: R. Shimon addresses Chachamim according to their reasoning. I obligate even for any amount of flour. You should admit to me about a wheat kernel, for it is a Briyah!

Chachamim say, an ant has a Neshamah, so it is a significant Briyah. A wheat kernel is not so important.

Chulin 96b (Mishnah): If the Gid ha'Nasheh was cooked with permitted Gidim, and we cannot recognize the Gid ha'Nasheh, they are all forbidden. Similarly, if a piece of Neveilah or Tamei fish (was cooked with permitted pieces... if we cannot recognize the Isur, all are forbidden).

99b - Question: The Gid should be Batel in the majority!

Answer: A Briyah is different (it is not Batel).

Question: The piece of Neveilah should be Batel in the majority!

Answer: It is not Batel because it is a Chatichah ha'Reuyah Lehiskaved (a piece fitting to honor guests with).

The Mishnah must teach both cases. Had it taught only about a Gid, one might have thought that a piece (of Neveilah) can become Batel. Had it taught only about a piece, one might have thought that a Gid can become Batel.

Mishnah (Terumos 10:8): If Tamei fish was pickled with Tahor fish, every barrel that holds two Sa'im, if it has the weight of 10 Zuz of Tamei fish, the brine is forbidden;

R. Yehudah says, a Revi'is in two Sa'im;

R. Yosi says, one part in 16.

Rishonim

Rambam (Hilchos Ma'achalos Asuros 15:34): If a Tamei fish was pickled with Tahor fish (brine), everything is forbidden unless the Tamei was one part in 200 of the Tahor.

Perush ha'Mishnayos (Terumos 10:8): The first Tana holds that if the Keli holds two Sa'im, and it was all Tahor fish except for 10 Zuz of Tamei fish, the brine is forbidden. If it was less than 10 Zuz, the brine is permitted. The Gemara explains that this is one part in 960. R. Yehudah forbids the brine only if there is a Revi'is of Tamei fish in two Sa'im. R. Yosi says that if the Tamei fish is one part in 16 of the Tahor fish, it forbids the brine. The Halachah is, if the Tamei is one part in 200, all the brine is permitted.

Ralbach (in Likutim in Frankel Rambam): The first Tana, R. Yehudah and R. Yosi hold, respectively, that Bitul is in 960, 192 and 16. The Rambam did not rule like any of them! Also, he should rule like the first Tana, whose opinion was taught Stam. The Yerushalmi rules like him. However, it added to require 1000. The Rambam ruled like this in his youth in Perush ha'Mishnayos, then retracted to say one in 200. He relies on Chulin 99b, in which R. Yosi bar Chanina says that the Shi'ur for brine is close to 200, i.e. like R. Yehudah. Also, R. Yehudah forbids Min b'Mino b'Mashehu, yet he holds that brine is Batel in 192, for it is a mere sweat, therefore, we should not more stringent than this. Also an opinion in the Yerushalmi rules like R. Yehudah. The Rambam was stringent to say 200, just like R. Yosi bar Bun was stringent to require 1000.

Rosh (Chulin 7:33): Some say that a Briyah is Batel in 960 parts of Heter. They learn from Terumos 10:8. If a Tamei fish was pickled with Tahor fish, every barrel that holds two Sa'im, if there is (the weight of) 10 Zuz of Tamei brine, the barrel is forbidden. The Yerushalmi says that this is one part in 960, for a Se'ah is 24 Lug, a Lug is two Litra, and a Litra is 100 Zuz. Two Sa'im are 9600 Zuz. R. Yosi bar Bun ruled b'Achbar (in a case involving a mouse) that it is Batel in 1000. He would have permitted in 960. This is unlike our Gemara, which equates a Briyah to a Chatichah ha'Reuyah Lehiskaved, which is not Batel even in 1000. We can say that it is equated to Chatichah ha'Reuyah Lehiskaved because such a large Shi'ur is needed for Bitul. Some say that 'Achbar' is a place, and the case involved brine, like the Yerushalmi was discussing. Presumably, a mouse did not fall in Heter. If it did, if one sees its form, one discards it and the rest is permitted. If it dissolved and one cannot taste it, it is Batel in 60.

Ran (Chulin Sof 36a): Some say that a Briyah is not Batel, i.e. in 60, but it is Batel in 1000. The Yerushalmi says that R. Yosi bar Bun ruled about a mouse, that it is Batel in 1000. R. Shimshon learned from a Mishnah that it is Batel in 960. This is wrong. Our Gemara equates a Briyah to Chatichah ha'Reuyah Lehiskaved. The Mishnah says that all are forbidden. A Tosefta (7:3) explicitly says that Chatichah ha'Reuyah Lehiskaved forbids even 1000. The same applies to a Briyah. Surely the Yerushalmi does not discuss Bitul of a Briyah. Sixty suffices to be Mevatel taste emitted by the Isur. The importance of a Briyah is only for itself (when it is intact), but not for its emissions. The Yerushalmi holds that a mouse gives taste up to 1000 parts. The Yerushalmi brought there that brine is Batel in close to 200. This is unlike the Bavli (Avodah Zarah 69a), which says that a mouse is Batel in 60.

Hagahos Ashri (Avodah Zarah 5:11): Bahag says that a Sheretz is Batel only in 1000. This is like the Yerushalmi. One should not rely on this, for our Gemara disagrees and says that it is Batel in 60.

Mordechai (Avodah Zarah 5:854): The Riva permits Nosen Ta'am li'Fgam (detrimental absorptions) even regarding Sheratzim, but a hidden scroll and the other Ge'onim say that we do not rely on our Gemara, rather on what was done in practice in the Yerushalmi, that a mouse is Batel in 1000. The Ri says that the Bavli is primary. Avi ha'Ezri received from his father that the Yerushalmi discusses brine, and Achbara is a place.

Rashba (1:270): Emissions of Gid ha'Nasheh are Batel in 60, but if the Gid itself was not dissolved, it forbids all the Gidin. A Briyah is not Batel. The Yerushalmi discusses Bitul in 960. The questioner said that this refers to the brine, but not the Tamei fish itself. What is his source? The Tana'im in the Seifa of the Mishnah argue about brine. Perhaps he assumes that the Reisha (a Tamei fish picked with Tahor fish) also discusses the brine. If it refers to Bitul of the fish itself, why must it mention that it was pickled? However, if it refers to brine, the first Tana, who says that it is Batel in 960, argues with R. Yehudah (who says that a Revi'is is Batel in two Sa'im, i.e. one part in 192) and R. Yosi (who says that it is Batel in 16). There cannot be such a large argument between the first Tana and R. Yehudah and R. Yosi. Also, he could not be so stringent about brine, an Isur mid'Rabanan and a mere sweat. After the Reisha, why does it say 'brine of a Tamei fish is forbidden' if the entire Mishnah discusses brine? Rather, there are three parts to the Mishnah. The Reisha discusses taste given off in pickling. The Mishnah is abbreviated. It says 'if a Tamei fish was pickled with Tahor fish', and did not give the law. The Seifa (every barrel...) discusses Bitul of the fish itself. The Seifa of the Seifa discusses Bitul of the brine. The Yerushalmi explained that we forbid in the Reisha, and that we require 960 for Bitul in the Seifa (of the fish itself). R. Shimshon explains this way.

Poskim

Shulchan Aruch (YD 100:1): A Briyah, such as an ant, Tamei bird, Gid ha'Nasheh, Ever Min ha'Chai or egg with a chick inside, or similar things, is not Batel even in 1000.

Beis Yosef (DH Yesh): Tosfos (Avodah Zarah 69a DH Idi) rules like the Rosh and Ran that a Briyah is not Batel in 1000. It seems that also the Rif and Rambam forbid, for they did not explicitly discuss this. Therefore, we are stringent.

Bach (3): R. Shimshon and Sha'arei Dura say that it is Batel in 960. The Maharshal explains that 960 is 16 times 60. The Mishnah says that Tamei brine is Batel 'Ad 16' (i.e. in 16 times more than other Isurim). Therefore, all this joins to be Mevatel a Briyah.

Gra (5): The Gemara equates a Briyah with Chatichah ha'Reuyah Lehiskaved. The latter is not Batel, for it is normally sold by number (Tosfos Avodah Zarah 74a DH Leme'utei). Perush ha'Mishnayos holds like the Rosh, that the Yerushalmi permitted brine in 960. The Mishnah Torah requires 1000.

Taz (101:12): Isur v'Heter ha'Aruch says that if a Briyah or Chatichah ha'Reuyah Lehiskaved was mixed b'Eino Mino, it lost its importance and it is Batel. This is unlike the Rashba, Rema and Shulchan Aruch (100:3), which forbids a pot of vegetables in which a Briyah was lost.