Copyright, 1918
By THE MACMILLAN COMPANY
Set up and electrotyped. Published, September, 1918
WHOM should this humble volume
seek to honor but the father and
mother whose unselfish devotion made
possible both my education and my
profession?
The highest type of scientific writing is that which sets forth useful scientific facts in language which is interesting and easily understood by the millions who read.
L. A. Mann.