 It is a rejection of the concept of spontaneous generation, which held that organisms could arise from nonliving matter.For example, maggots were believed to appear spontaneously in decaying meat; Francesco Redi carried out experiments that disproved this notion and coined the maxim "Omne vivum ex ovo" ("Every living thing comes from a living thing" — literally "from an egg"); Virchow (and his predecessors) extended this to state that the only source for a living cell was another living cell.In 1845, Virchow and John Hughes Bennett independently observed abnormal increases in white blood cells in some patients.