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Edward Jenner and the Control of Smallpox         Edward Jen…

Edward Jenner and the Control of Smallpox         Edward Jenner (1749–1823) was a physician in western England during the late 18th and early 19th centuries. At that time in Europe and Asia, smallpox was a common disease. Many children died of it, and many who survived were disfigured by scars. It was known that people who had survived smallpox were protected from future infection. It became common practice in those days to deliberately expose healthy children to smallpox.  A less severe form of the disease usually developed and children were protected from future smallpox infections. In 1796, Jenner discovered a safer way to protect against smallpox.  As a physician he often treated milkmaids and other farmworkers who developed a mild illness known as cowpox.  Cowpox caused pox-like sores on the milkmaids’ hands after milking cows with cowpox sores on their teats. Jenner noted that very few of those milkmaids and farmworkers who had been infected with cowpox became sick with smallpox. He asked the question, “Why don’t people who have had cowpox get smallpox?”  Jenner performed an experiment. He took pus-like material from a sore on the hand of a milkmaid named Sarah Nelmes and rubbed it into small cuts on the arm of an 8-year-old boy named James Phipps. James developed the normal mild infection typical of cowpox and completely recovered. Later, Jenner inoculated James and another boy, Larry, with material from a smallpox patient.  (Recall that this was a normal practice at the time.) James did not develop any disease.  Larry developed a case of smallpox.  Jenner’s conclusion was that deliberate exposure to cowpox had protected James from smallpox. Eventually the word vaccination was used to describe the process. It was derived from the Latin words for cow (vacca) and cowpox disease (vaccinae). Adapted from Enger. Copyright 2012 Concepts in Biology. 14th Edition. McGraw-Hill How Science Works 1.1 p. 18   In the experiment, what was the independent variable?