To the Editor: —With all our fresh air propaganda is it not strange that the sterilizing and operating rooms of our city seem never to have profited by it? I have assisted or operated in five Chicago hospitals and have witnessed operations in seven others, and in none of the operating rooms was there any evidence of scientific heating and ventilation such as may be found in public schools and other buildings. Postoperative pneumonia is considered due to chilling of the patient, but I believe the vitiated atmosphere of the operating room may have a devitalizing influence on the patient. When you consider the amount of fresh air that is necessary to keep the carbon dioxid below the safety limit, it is strange that more patients do not succumb. The operator dreads a draft of air which sends dust flying, with the chance that each particle of dust is an