People and utensils [both] become tamei from a corpse. People have a stringency that utensils do not have, and utensils have [a stringency] that people do not have. [When a] utensil [touches a corpse,] three [utensils will become tamei in turn after the first utensil touches a corpse], whereas [when] a person [becomes tamei by touching a corpse, only] two [will become tamei]. People have a stringency [that utensils do not have]: When a person is in the middle, there can be four [persons and utensils that become tamei in succession], but when there is no person in the middle, there can be only three [stages of con-tact].