Chullin 51 - Blind Pouch, Reticulum
Reticulim is the second compartment of the stomach. If it is punctured from the outside, the animal is a terefah. If a needle was found it in, and it goes through both walls, the animal is a terefah, provided that the puncture occurred while the animal was still alive. A drop of blood can testify to that. However, if a scab formed over the opening of the puncture would, then it is clear that the puncture occurred more than three days before. Thus the animal was terefah when one bought it, and he can ask for his money back.
If an animal fell from a roof, it is considered terefah without any further signs, unless it survives for the next twenty-four hours.
Art: Joseph Crawhall - Pigeons on the Roof
