Heisenberg uses Dirac's method for the calculation of certain quantities. The concept of polarization of vacuum is not defined according to this theory.

Pauli comments on a manuscript by Heisenberg. The important progress lies in the recognition of the fact that all infinities are created by the field quantization. Mathematically things are satisfactory, but physically, no experimental consequences can be expected, because the neglect of the radiation-reaction forces is not legitimate. He remarks on coherent scattered radiation and on Weisskopf's and Delbrück's work on it. He writes of his thoughts on the significance of e$^{2}/(h.c) and of the concept of charge and its conservation.

Heisenberg does not think that substraction physics makes sense. He writes about what he has learned of nuclear physics in Copenhagen, about the order of magnitude of exchange forces, and Bethe's suggestion to replace Fermi's relation for interaction by another. He writes about the explanation of all mass defects by a plausible exchange force and he belives that the theory of the positron and quantum electrodynamics should be brought in order before attacking nuclear problems.

Pauli replies to questions from Heisenberg in his letter of 4 November 1934. The self-energy of the electron in Pauli's theory becomes logarithmically infinite . This theory can only be developed with Bose-statistics. He writes about the Lagrange function of the scattering of light by light and about the magnetic moment of the neutron and the symmetry of the laws of nature with regard to the sign of the charge. He talks about the magnetic moment of the proton and the deuteron.

Pauli agrees with Heisenberg's letter of the 23 May which clarifies the question of decidability between various laws of force in proton-neutron scattering.

Pauli is glad that Heisenberg's last letter of the 1st May has clarified the problem of frequency dependence of additional terms in Heisenberg's equation. He gives an outline of his paper for the Solvay congress.

Pauli replies to a letter by Landé criticizing a theory which he develops.

Pauli expresses his enthusiasm over Dirac's Bakerian lecture and makes several comments on it.

Pauli writes about the magnetic moment with strong coupling in the meson theory. He comments on the two-nucleon problem.

Pauli says that the magnetic moment of the triton can only be accounted for by the use of exchange current.