Chullin 56 - June 25, 10 Tamuz

The Mishna enumerates all the physical defects that cause a bird to be rendered a treifa, as well as those that leave it kosher. If a weasel (chulda) attacks a bird in an area where the brain membrane could have been perforated, the bird is considered a treifa. There are, however, different tests one can perform to ascertain whether the membrane was actually punctured, and the Gemara suggests various methods for this inspection. Conversely, in the case of birds that live in the water, a broken skull creates an absolute presumption that the brain membrane was punctured, meaning that no subsequent test will be effective in permitting the bird. If a bird was caught in a fire and burned, the Gemara outlines specific ways to determine whether its internal organs were affected to the point of rendering the bird a treifa. This diagnostic procedure relies on checking for a change in color - either from red to green, or from green to red, depending on the specific internal organ being evaluated. Following the Mishnaic list of kosher conditions in a bird that do not render it a treifa, the Amoraim introduce specific qualifications and limitations to restrict the scope of some of these permitted cases.