Hullin 57: Scientific Experiments - Talmud Style: No King at the Ant Hill
If a bird has a dislocated femur, the bird is nonetheless kosher. But it seems that the same sage said that it was not kosher - in Pompedita, leading to an observation that different stringencies applied in different communities. One element of the decision being where the break occurs in the bird's leg. [Who's Who: Rabbi Shimon bar Halafta] Also, efforts to demonstrate that an animal that had been dubbed a treyfa is really not a treyfa - experiments by R. Shimon bar Halafta to disprove Rabbi Yehudah, including the shenanigans at an ant hill that apparently has no king.
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