2. LEMMA 1. [31 p. 132. Let C be the rectangle whose vertices are iT, -iT, T + iT, T iT running in the positive direction. Let us put F(z) = log cD(-iz), where z = x + iy, the logarithm being defined as follows; we start with a particular determination on x = T and it is real when z = T, and obtain the value at other points by continuous variation along y = constant from log 4D(-i(T + iy)). If, however, this path would cross a zero of 4( -it) we put, [3] p. 132, F(z) = 1 lim {F(z + ie) + F(z -ie). '6-0