On the plasticity of crystals

A. Smekal(1) recently in a letter to The Physical Review is still advocating the idea that microscopic crevices are the essential cause of the peculiar mechanical and plastic behavior of rocksalt and crystals in general. Although conclusive evidence has repeatedly been brought forth by myself and other writers that Smekal's "imperfection" theory does not account for some of the most essential physical properties of crystals, his remarks in the mentioned letter require some comment.