SCIENCE PROGRESS 



IN THE TWENTIETH CENTURY 



A QUARTERLY JOURNAL OF 



SCIENTIFIC WORK 



& THOUGHT 



EDITOR 



SIR RONALD ROSS, K.C.B., K.C.M.G., F.R.S., 

 N.L., D.Sc, LL.D., M.D., F.R.C.S. 



ASSISTED BY 



D. ORSON WOOD, M.Sc, A.R.C.Sc, and 

 J. BRONTE GATENBY, B.A., B.Sc, D.Phil. 



VOL. XV 

 1920 — 1921 



LONDON 

 JOHN MURRAY, ALBEMARLE STREET, W. 



1921 



