One of the most fundamental problems in elementary particle physics is the study of the interaction of the pion meson with nucleons. It is believed that the pion meson plays a fundamental role in the description of nuclear forces and it is important, therefore, to understand the interaction of these particles. The primary method of gaining information on this interaction is through scattering experiments, and this book is concerned primarily with studies of pion-nucleon scattering at high energies. Originally published in 1969. The uses the latest print-on-demand technology to again make available previously out-of-print books from the distinguished backlist of Princeton University Press. These editions preserve the original texts of these important books while presenting them in durable paperback and hardcover editions. The goal of the Princeton Legacy Library is to vastly increase access to the rich scholarly heritage found in the thousands of books published by Princeton University Press since its founding in 1905.