Heisenberg asks questions about the theory of holes.

Heisenberg writes about Pauli's objections to his exchange-relations.

Heisenberg revokes his remarks made in the last letter.

Heisenberg gives new calculations about the theory of holes. He writes about the gauge-invariance of certain expressions, about the problem of self-energy. he talks on the necessity for theories with infinite degrees of freedom and a quadratic wave equation should be possible in the case of absence of external fields.

Heisenberg gives a few corrections to the last letter.

Heisenberg sends a manuscript describing the present situation of the theory of holes. He expresses the hope that the way from this theory to the explanation of $^{2}$/(h.c) will be short.

Heisenberg talks about his attempts to find the value for e$^{2}$/(h.c.) by a suitable holes theory.

Heisenberg writes on a typical difference betwen quantum electrodynamics and Fermi's Beta-Decay theory. The existence of cosmic ray showers can possibly be explained by Fermi's theory. He gives numerical calculations.

Heisenberg talks about some plausibility arguments against Pauli's objections and about a possible solution for the interaction of neutrinos in the case of many particles. He writes about an application of a kind of Thomas-Fermi-method for the state of lowest energy. From this interaction the production of showers can possibly follow.

Heisenberg gives a description of the present situation of the field-theory. In a more complete future theory there will exist no particles smaller than the universal length, and the divergences of the present theory will be avoided. He writes about more considerations about nuclear theory. The pair production observed up to now can only be interpreted as internal emission. About an experimental paper on shower production in great depth.