Malaria and yellow fever came from swampy areas. Properties of water should be closely observed. Hot and cold diseases: ex: diarrhea was considered a hot disease, and would be treated with a cold treatment such as fruit. Atomic theory everything is made up of tiny particles: earth atoms, air atoms, water atoms, and fire atoms. Sydenham came up with the three levels of fevers; continued fevers, intermittent fevers, and smallpox. He also advanced useful treatments such as exercise, fresh air, and a healthy diet, which other physicians dismissed at that time. Scurvy is characterized by bleeding gums, bleeding under the skin, and extreme weakness. Lind observed the mariner"s diet and saw that the sea diet was extremely gross and hard on digestion. Noticed his milkmaids did not contract smallpox. Smallpox is characterized by a headache, backache and eruption of blisters. Milkmaids got cowpox but never got small pox.