Heisenberg attempts to justify his axiomatics and to show that it is less arbitrary than suspected by Pauli.

Heisenberg replies to a question by Pauli concerning certain equations in his last letter.

Heisenberg talks about a paper by himself and Ascoli on the fine-structure constant. He comments on a paper by Källén and Glaser in which the V-particle of the Lee-model becomes radioactive, disintegrating into N and $\Theta$.

Heisenberg talks about his recent results giving tentative proof that in all sectors of the Lee model with dipole ghost the S -matrix is unitary.

Heisenberg writes on clarification of the question of the existence of a solution for the integral equation containing a simple pole. He gives his opinion on Källén's calculations.

Heisenberg remarks on Pauli's letter of the 25 and the 27 December, especially on invariance properties of the group.

Heisenberg writes about his new results about the nature of the $\Pi$-meson. He writes about the reformulation of their preprint.

Heisenberg expresses his regret at Pauli's letter telling of Pauli's withdrawal from the work. He gives additional comments on the results. He does not want to publish the pre print if Pauli does not appear as co-author.

Heisenberg writes about the Einstein - de Haas effect, the failure of Bohr's theory of He, his own work with Born and about Lande's theory of multiplets.

Heisenberg writes on the recent Göttingen theory of the anomalous Zeeman effect.