VOLUME 5 
APRIL, 1919 
NUMBER 4 
PROCEEDINGS 
OF THE 
National Academy 
OF Sciences 
OF THE 
UNITED STATES OF AMERICA 
EDITORIAL BOARD 
Raymond Pearl, Chairman 
C. G. Abbot, Acting Home Secretary 
Edwin B. Wilson, Managing Editor 
George E. Hale, Foreign Secretary 
J. M. Clarke 
H, H. Donaldson 
E. B. Frost 
R. A. Harper 
LuDViG Hektoen 
H. S. Jennings 
Jacques Loeb 
Graham Lusk 
A. G. Mayor 
R. A. MiLLIKAN 
E. H. Moore 
A. A, NoYES 
W. A. NOYES 
E. L. Thorndike 
W. M. Wheeler 
Publication Office: Williams & Wilkins Company, Baltimore 
Editorial Office: Massachusetts Institute of Technology, Cambridge 
Home Office of the Academy: Washington, D. C. 
JIHISi 
I as second-class matter at the postoffice at Baltimore, Maryland, under the act of August 24, 1912. Acceptance for mailing at special 
rate of postage provided for in Section;^ 1103, Act of October 3, 1917. Authorized on July 3, 1918. 
Price per annum, $5.00 
