The following occurred: a young girl had opened the stomach of a [properly slaughtered] chicken in order to clean it out, on the edge of a table. A cat stood below, anticipating that might eat whatever would fall to the ground. Afterwards, the girl claimed that she did not find the chicken's heart. The mother of the girl said it was possible - in fact, almost certain - that the heart had been [accidentally] thrown to the ground and eaten by the cat, which was excited to eat whatever came close to it. The girl insisted that she did not give the heart to the cat. The chicken was fat, healthy, and good; there was nothing abnormal, nor was anything torn in its innards. There was no indication that its heart had shrunk or melted - nothing at all was abnormal in all of its innards. While it had been alive, it was strong, healthy, and had all the normal koach, eating and drinking, walking and flying. It had all of its normal function, was at full strength: in short, it was as healthy as all other healthy chickens. However, the girl insisted that she did not find the heart.
This case came before the sages, and they deemed the chicken "treif", for the reason that it was missing its heart. We would ask of the Teacher, what is the ruling regarding this chicken?
Answer: All those who claim that the chicken was treif are in error. For it is clear to all whose hearts are wise, and whose brains are sharp, that it is impossible for any animal in the world to live, for even a moment, without a heart, as if they were healthy. One cannot imagine such a situation. Rather, as soon as the heart is cut out of a creature, they have been slaughtered. And what about the possibility that there had been sickness? It is impossible to say that the heart had shrunk, or melted, without the creature having been incredibly sickly. And yet this chicken wasn't sickly or ill; on the contrary - it was fat, healthy, good, and normally functioning! The matter is clear, that the heart fell out of the opening in the stomach, and that the cat ate it. This is indeed so obvious, that it does not require proof.
However, to silence the mouths of the idiots who are so eager to rule in this case, I cite the ruling of the Kessef Mishna, the Laws of Slaughter (10), who gives a reason why Maimonides did not list "missing heart" or "born without a heart": limbs which, were they to be removed, the animal could not live for even a moment, [Maimonides] did not list them.