Observations suggest questions to investigate. In the summer of 1897 an English physician, Ronald Ross, worked in a remote field hospital in Secunderabad, India. Ross set out to find the cause of malaria. Of all tropical diseases, malaria was the greatest killer, taking more than a million lives a year in India alone. No one knew what caused the disease - but most doctors thought it was brought about by poisonous mists or vapors. Working alone, Ross discovered the pattern by which the disease spread. Ross observed that patients in the field hospital who did not have malaria were more likely to develop the deadly disease in the open wards (those without screens or netting) than in wards with closed windows or screens. Ross wondered why people in open wards were much more likely to get malaria than those in closed wards. In searching for the cause of malaria, what observations did Ross make about the location of patients who developed the disease in the field hospital?