“…and Nichols,8 and Chalmers and Christopherson ; 9 and finally we are indebted for elucidating studies to the contributions of Schamberg, 10 Ormsby and Mitchell, 11 Guggenheim,12 Fabry,13 Hudelo,14 Mitchell,15 Greenbaum and Klauder, 16 Hicks and Chopping,17 and others.…”