Heisenberg writes about the paper of Born and Wiener, and on cyclical variables.

Heisenberg writes about cyclical variables and the consequences for Goudsmit's hypothesis.

Heisenberg comments on his note on fluctuations which he wrote against the continuum-conception of Schrödinger. He talks about Dirac's ideas on relativistic formulation of Schrödinger's equation, and gives his thoughts on ferromagnetism and conductivity.

Heisenberg agrees with Pauli's calculations on the spinning electron in his last letter. He writes about Dirac's generalization of the transformation function S, and its physical content. He thinks that Dirac's work is a very great step forward. He writes also about Hund's work on H$\p2$, two calculations by Sugiura, on the number of dispersion electrons in Na, and on the continuous spectra of H.

Heisenberg asks questions about the perturbation theory of the relativistic Schrödinger equation, about the mathematics of the electron spin and about spin and structure of the nuclei. He writes about his criticism of a paper by Ehrenfest on attraction and repulsion of spinning electrons, and about his own occupation with the logical foundation of the pq - qp formalism.

Heisenberg writes about the difficulty with the assumption of a Gaussian distribution for the energy values in his calculations.

Heisenberg replies to two letters from Pauli about empirical data of nuclear moments. He writes about the rule of Fermi and Segrè. He talks about Pauli's idea of the existence of two kinds of neutrons and on the possible types of nuclear forces, about Ehrenfest's death and about Planck's philosophy of science.

Heisenberg writes more about the theory of holes and about another method for the elimination of an infinite charge density.

Heisenberg asks some questions in connection with Pauli's letter. One of Heisenberg's assumptions for space-like vectors is incompatible with the differential form of the conservation laws, and the latter has to be renounced which makes sense. He gives some remarks about Fermi's paper and the interaction introduced by him.

Heisenberg replies to Pauli's letters. He writes about a future formulation of field theory, where matter and radiation fields will appear as different properties of the same field. He talks of Pauli's remarks that the exchange relations of electrical and magnetical field strengths have to be modified.