Chullin 73 - A Dangling Limb
A dangling limb is a limb that is somewhat detached from the body of an animal and is connected to it by a strip of flesh. If the limb can heal, then it is treated as part of the animal and is rendered permissible by the animal's kosher slaughter. However, if it cannot heal, then we have the following disagreement.
Resh Lakish says that the dangling limb is similar to a limb of a fetus protruding from its mother's womb, and it is subject to the disagreement between Rabbi Meir and the Sages . Rabbi Yochanan says that in the case of a dangling limb there is no disagreement, but rather it is considered attached to the body of the animal, and shechitah makes it permitted for consumption and free from impurity - except that the Sages later forbade to eat it. By contrast, if the animal with a dangling limb dies by itself, the limb is considered to have been detached before death, and its impurity is less than of a nevelah. How so? A piece of meat separated from a torn limb is pure, while a piece of meat separated from an animal that died by itself is impure.
Art: William Huggins - Rams and Ewes in a Landscape