Chullin 42 - These Are The Cases of Terefah
The Torah said, " Do not eat flesh torn off in the field by a predator ." This cannot mean that the animal already died by itself - for then it would be a case of nevelah, carcass. Rather, it is talking about an animal that is fatally wounded. Even if it was properly slaughtered, it is forbidden to be eaten as "terefah." The defect may be caused by an animal or a man, in any place, it can even be congenital, and "in the field" simply describes a common scenario.
There are eight general categories of terefah , taught to Moses on Sinai, and they can be arranged according to the Hebrew acronym of "dan chanak nefesh(דן חנק נףש)." They are: clawed, punctured, deficient, removed, torn, fallen, severed, and fractured. For practical purposes the classification of terefah was divided into eighteen cases, starting with an animal whose esophagus was punctured, one whose trachea was severed, whose brain was punctured, and so on.
The laws that follow are complex, and the difficulty is compounded by the fact that not everybody knows the necessary details of the animal anatomy . Artscroll illustrations can help.
Art: George Frederick Watts - The Wounded Heron