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.
The theory of evolution by natural selection that was developed by Charles Darwin revolutionized the study of living things. In his Origin of Species (1859) he provided a scientific explanation of how the diverse species of plants and animals have descended over time from common ancestors.