Heisenberg writes about recent developments in the formalism of quantum mechanics, perturbation theory and some results for systems with axial symmetry.

Heisenberg writes about the problem of continuous spectra from the point of view of quantum mechanics. The effect of time dependent external forces on the atom, and Jordan's calculations of the statistical behaviour of proper vibration of a membrane according to the new theory.

Heisenberg writes about the compatibility of Goudsmit's hypothesis with the formalism of Heisenberg.

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.

Pauli writes about the necessity of equal treatment of space and time coordinates in relativistic quantum mechanics. He talks about the impossibility to explain quantum phenomena with concepts of continuum physics alone. He comments

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.