But if it is on the back of the lung, even if it is as small as a myrtle leaf, the animal is a tereifa.

§ Rafram says: This lung that is similar to a chip of wood renders the animal a tereifa. There are those who say that the similarity lies in its appearance, i.e., if it is pale like wood. And there are those who say that it lies in its feeling, i.e., if it is hard like wood. There are those who say that it is swollen. And there are those who say that it is light. And there are those who say that it is completely smooth, that it has no sectioning of lobes.

§ Rava says: If the lung assumed a dark color like eye shadow, the animal is kosher. If its color is black like ink, the animal is a tereifa. As Rabbi Ḥanina says: Menstrual blood that appears black is actually red, except that it decayed. Black color is therefore a sign of decay, and the lung is assumed to be defective.

The Gemara continues: If the lung was green, the animal is kosher, as can be derived from the episode of Rabbi Natan. And if it was red, it is kosher, as can be derived from the episode of Rabbi Natan. As it is taught in a baraita: Rabbi Natan says: Once I went to the cities overseas, where one woman came before me who circumcised her first son and he died, and she circumcised her second son and he died, and out of concern that circumcising her third son might cause him to die as well, she brought him before me. I saw that he was red, so I said to her: My daughter, wait for him until his blood is absorbed into him. She waited for him until his blood was absorbed into him and then circumcised him, and he survived. And they would call him Natan the Babylonian after my name. This incident indicates that a red lung can heal.

Rabbi Natan further related: And on another occasion I went to the state of Cappadocia, and a woman came before me who circumcised her first son and he died, and she circumcised her second son and he died. Out of concern that circumcising her third son might cause him to die as well, she brought him before me. I saw that he was green, i.e., pale. I looked at him and saw that he did not have the blood of circumcision in him, i.e., he had a deficiency of blood such that no blood would emerge from the circumcision. I said to her: My daughter, wait until his blood enters him. She waited for his blood to increase and then circumcised him, and he survived. And they would call his name Natan the Babylonian after my name. This incident indicates that a green lung can heal as well.

Rav Kahana says: If the lung has an appearance like the liver, the animal is kosher. If it has an appearance like flesh, the animal is a tereifa. And your mnemonic to remember that the latter is a tereifa is the verse: “You shall not eat any flesh that is torn of animals [tereifa] in the field” (Exodus 22:30).

Rav Sama, son of Rava, says: This lung whose appearance resembles dodder, or saffron, or has a yellow color such as that of an egg yolk, renders the animal a tereifa. Since all of these appearances are various shades of green, the Gemara asks: But the green lung that is kosher, what is it like? The Gemara responds: It is like a leek.

§ Ravina says: If there was a sealed area in the lung that does not inflate, we bring a knife and tear it open. If there is pus in the sealed area, then it was definitely sealed due to the pus, and the animal is kosher. But if we do not find pus there, we lay a feather or saliva on the opening and inflate the lung. If the saliva bubbles or the feather moves, the animal is kosher, since some air does reach the area, and if not, there is some defect in the lung, and the animal is a tereifa.

Rav Yosef says: A membrane that appeared due to a wound in the lung, i.e., a scab that covered a perforation through the lung, is not considered a true membrane, since it does not last. And Rav Yosef says: With regard to this lung that emits a sound when inflated, if we know from where it emits a sound, we set a feather, or straw, or saliva on that point. If the saliva bubbles when the lung is inflated, the animal is a tereifa, since this proves that the lung is perforated through both membranes. And if not, the animal is kosher. And if we do not know from where it emits a sound, we bring a basin of tepid water and set the lung inside it.

One cannot place it in hot water, as it causes the lung to contract, closing the perforation. And one cannot place it in cold water, as it hardens the lung and may cause it to crack. Rather, we check it in tepid water. If the water bubbles, the animal is a tereifa. And if not, the animal is kosher, since it is apparent that only the inner membrane is perforated and the outer membrane is not perforated, and the fact that it emits a sound is due to the air moving in the space between the two membranes.

§ Ulla says that Rabbi Yoḥanan says: An animal with a lung that liquefied and can be poured out like water from a jug is kosher. The Gemara notes: Evidently, Rabbi Yoḥanan holds that a deficiency on the inside of an organ is not considered a deficiency. Only a deficiency in the wall or membrane of an organ renders an animal a tereifa.

Rabbi Abba raised an objection to Ulla from the mishna, which states: The lung that was perforated or that was missing a piece renders the animal a tereifa. What is the case of a lung that was missing a piece? If we say that it was missing a piece on the outside, this is the same as if it was perforated, since any missing piece of the lung wall would constitute a perforation. Rather, is it not referring to a missing piece on the inside? If so, learn from the mishna that a deficiency on the inside of an organ is considered a deficiency to render the animal a tereifa.

The Gemara responds: No, the mishna actually is referring to a missing piece on the outside. And with regard to that which you said: This is the same as if it was perforated, one may respond that no, it is necessary to mention both cases to account for the opinion of Rabbi Shimon in the mishna, who says: It is not a tereifa until the lung is perforated through to the bronchi. By mentioning both cases, the mishna teaches that this statement of Rabbi Shimon applies only to a small perforation that does not constitute a deficiency. But in the case of a perforation so large that it constitutes a deficiency, even Rabbi Shimon concedes that it renders the animal a tereifa even if the perforation does not reach the bronchi.

The Gemara relates that Rabbi Ḥananya became sick. Rabbi Natan and all the eminent scholars of the generation entered before him to visit. They brought before him a lung that could be poured out like water from a jug, and he deemed the animal kosher.

Rava said: This is the halakha only if the bronchi still exist and only the flesh of the lung has liquefied. Rav Aḥa, son of Rava, said to Rav Ashi: From where do we know whether the bronchi still exist? Rav Ashi said to him: We bring a glazed earthenware vessel with no cracks, so the contents can be observed, and we pour the lung into it. If there are white streaks in it, the animal is a tereifa, as the white streaks are remains of the liquefied bronchi. And if not, the animal is kosher.

Rav Naḥman says: If the lung was partially atrophied and only part of the flesh remains, but its membrane still exists, the animal is kosher. The Gemara notes: This is also taught in a baraita: If the lung was atrophied, but its membrane still exists, even if the space vacated by the atrophied lung can hold a quarter-log of fluid, the animal is kosher.