from the Office of industrial Hygiene and Sanitation, Surg. R.R. Sayers, medical office in charge ; engineering studies by J.J. Bloomfield ..., J.M. DallaValle ... ; medical studies by R.R. Jones ..., Waldemar C. Dreesen ... ; statistical analysis by Dean K. Brundage ..., Rollo H. Britten ... ; with sections on autopsy material by J.W. Miller ... and on silica in the urine and in lung specimens by F.H. Goldman ... ; prepared by direction of the Surgeon General