Integration is now very successful in the field of life sciences: neuroscience, physiology, and a whole part of biology claim to be “integrative.” The term appears in the titles of scientific journals: Integrative Biology, Integrative and Comparative Biology, OMICS: A Journal of Integrative Biology, etc. However, this situation results from a complex genealogy. Initially mathematical like the notion of function, the concept penetrated into the field of life sciences in the second half of the nineteenth century. Its history meets simultaneously Herbert Spencer’s evolutionism and Claude Bernard’s physiology. It will take a more specific meaning in John Hughlings Jackson’s, David Ferrier’s, and especially Charles Scott Sherrington’s neurologies. The following contesting of the Sherringtonian paradigm will not prevent the development of the notion in general physiology at John Barcroft’s instigation. We suggest here investigating the successive rectifications of the concept of integration, which every time express a different vision of the body and successively a strategy to be adopted to elucidate its physiology.