C. difficile diarrhea is largely a nosocomial disease and is the most frequent cause of diarrhea in hospitalized patients. Its occurrence in the outpatient setting, other than in patients confined to nursing homes, is much less common.
Darwin had arrived at a complete theory of evolution by 1839, but it was to be another 20 years before he published his ideas of evolution through natural selection in his epochal book On the Origin of Species by Means of Natural Selection.
Darwin's theory of evolution. The basic idea behind the theory of evolution is that all the different species have evolved from simple life forms. These simple life forms first developed more than three billion years ago - the Earth is about 4.5 billion years old.