10 
We have again profited by the cooperation of Dr. W. C. Woodward, 
the health officer of the District of Columbia, and also the officers of 
the filtration plant. We are indebted to the hospitals throughout the 
city and to many physicians for help in the epidemiological studies. 
In drawing up the conclusions and recommendations of this report 
we have had the benefit of consultation with the advisory board of 
the Hygienic Laboratory, composed of eminent scientists and sani- 
tarians. This privilege is appreciated, and we desire to acknowledge 
the help we have received from the members of the board collectively 
and individually. 
M. J. Rosenau, 
Director Hygienic Laboratory ^ Chairman. 
L. L. Lumsdex, 
Passed Assistant Surgeon. 
Joseph H. Kastle, 
Chief of Dirision of Chemistry^ Recorder.^ 
United States Public Health and Marine -Hospital Service. 
