Vaccination. The arm of Sarah Nelmes, a dairy maid, who had contracted cowpox. ... Recognizing that dairymaids infected with cowpox were immune to small-pox, Jenner deliberately infected James Phipps, an eight year old boy, with cowpox in 1796. He then exposed Phipps to smallpox–which Phipps failed to contract.
the respiratory system and the circulatory system work closely together to deliver oxygen to cells and to get rid of the carbon dioxide the cells produce.
