Heisenberg makes some remarks on Fermi's paper. He writes on his matrix elements for pair creation and gives some calculations about the exchange energy of proton and neutron.

Heisenberg expresses doubts about the theory of holes; Pauli's schema is logical, but too complicated and a bit arbitrary. The questions are: "Are the expectation values for charge-and energy-density finite?" "Are the latter not occasionally negative?"He writes about the latest results of de Broglie and Joliot-Curie.

Heisenberg replies to Pauli's questions on the possibility of calculating the total energy of matter created by the introduction of fields. He gives suggestions for the improvement of the paper and talks about Pauli's theory regarding the Klein-Gordon equation and the possibility of finding by this a method of field quantization, provided that modifications are introduced in the quantization rules of field, leading to spinors and Fermi-statistics. He writes about the scattering of light by light.

Heisenberg replies to Pauli's and Weisskopf's letters about the self-energy of the photon.

Heisenberg writes in order to proceed with electrodynamics. One has to know the consequences of the present formalism. He asks for Pauli's opinion.

Heisenberg writes on Bohr's forthcoming reply to Einstein's thought experiment (screen and two diaphragms) concerning causality and quantum theory. He talks of his own plans for a paper on nuclear physics.

Heisenberg does not agree with Pauli about the identical situation of quantum electrodynamics and Fermi's theory, because the latter contains a universal constant of nature. He says that for high energies one has to expect completely different results. He writes that is the shower-formation is as an important consequence of Fermi's theory.

Heisenberg agrees with Pauli that the mathematical problems should be approached by a limiting process from the lattice-world. He gives some suggestion for a Hamiltonian scalar theory. He talks about a common trip to Copenhagen.

Heisenberg believes that Pauli's proof of the infinity of eigenvalues is not cogent.

Heisenberg reports on the results of his investigation on the mathematical properties of Pauli's lattice world. He believes that further investigation on this model is worthwhile.