William Mansfield Clark, Ph.D., headed one of our oldest laboratories, the Laboratory of Chemistry in the Hygienic Laboratory, a precursor of the NIH, from 1920 to 1927. He conducted basic studies on oxidation reduction and the health hazards of tetraethyl lead, part of the foundation of today's research on industrial and environmental hazards of toxic substances. He left the NIH to become the head of physiological chemistry at Johns Hopkins University in Baltimore. Dr. Clark was elected to the National Academy of Sciences in 1928. | 
