Professor A. Landé has kindly sent me a manuscript of a paper in which he develops some most important ideas on the meaning and the value of the number 137. His work is founded on the principle of reciprocity which I recently suggested (Born, 1938). Landé adds to this principle a new assumption about the wave functions, representing an electron, and he finds a linear integral equation for these containing a parameter the value of which may be expected to be 137. It is Landé's great merit to have shown that the reciprocity principle leads to a condition for the Planck constant ћ (the value of which in natural units, c = 1, e = 1, is 137), and to have discovered the root of the peculiar order of magnitude of the number. But some difficulties which I encountered led me to reconsider the problem.