The Mishnah noted that the Torah states (in and ) the characteristics of domestic and wild animals (by which one can tell whether they are clean). The Mishnah noted that the Torah does not similarly state the characteristics of birds, but the sages taught that every bird that seizes its prey is unclean. Every bird that has an extra toe (a hallux), a crop, and a gizzard that can be peeled off is clean. Rabbi Eliezer the son of Rabbi Zadok taught that every bird that parts its toes (evenly) is unclean. The Mishnah taught that among locusts, all that have four legs, four wings, jointed legs (as in ), and wings covering the greater part of the body are clean. Rabbi Jose taught that it must also bear the name "locust." The Mishnah taught that among fish, all that have fins and scales are clean. Rabbi Judah said that it must have (at least) two scales and one fin (to be clean). The scales are those (thin discs) that are attached to the fish, and the fins are those (wings) by which it swims.