during life, by the processes of eating and digesting, the matter composing the body undergoes perpetual change.
 Bertrand Russell, A History of Western Philosophy (1945). copy citation

Context

“I am happy to say that this difficulty, which might at first sight seem insuperable, is triumphantly met. The identity of the body, Saint Thomas points out, is not dependent on the persistence of the same material particles; during life, by the processes of eating and digesting, the matter composing the body undergoes perpetual change. The cannibal may, therefore, receive the same body at the resurrection, even if it is not composed of the same matter as was in his body when he died. With this comforting thought we may end our abstract of the Summa contra Gentiles.” source