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.
Patterns of species' ranges. Wallace had already accepted evolution when he began his travels in 1848 through the Amazon and Southeast Asia. Wallace came to much the same conclusion that Darwin published in the Origin of Species: biogeography was simply a record of inheritance.