Bechoros 6:6

It’s a blemish if an animal has no testicles, or just one. Rabbi Yishmael says that if the animal has two pouches, it has two testicles but if it only has one pouch, then it only has one testicle. Rabbi Akiva says that if an animal with two pouches but apparently only one testicle is sat and the pouch squeezed, the second testicle will ultimately emerge, assuming there is one. It once happened that the pouch was squeezed and a second testicle did not emerge (so it was ruled a blemish). When the animal was slaughtered, the second testicle was found stuck to the animal’s loins. Rabbi Akiva permitted the animal to be eaten (since the second testicle had not emerged) but Rabbi Yochanan ben Nuri prohibited it (since the animal did, in fact, have both testicles).

Bechoros 6:7

An animal is considered blemished if it has five legs or three, if its feet are uncloven like a donkey’s, or if it has a dislocated hip or one that is higher than the other.