The opposition between mechanism and vitalism is an old and venerable one. It seems to be particularly active in the hands of historians of biology, particularly late nineteenth and early twentieth-century biology (Hein 1972, Allen 2005). Broadly speaking, histories of biology and medicine endlessly and ceaselessly oppose mechanism and vitalism, usually focusing on the most dogmatic pronouncements of both such perspectives (iatromechanistic rhetoric and immaterial vital forces). Thereby they neglect the fertility and diversity of types of early modern mechanism (a diversity noted in Des Chene 2001; see also Hutchins 2015, Wolfe 2014), including as attempts to do justice to the ontological status of Life itself, and conversely, the mechanism-friendly dimensions of core moments of vitalist theorization, notably in the notions of 'organisation' and 'animal economy' in Montpellier vitalism (Wolfe and Terada 2008, Wolfe 2017a, 2019a). Furthermore, the opposition between mechanism and vitalism effectively obscures the singularity and the importance of specifically structural concepts, which are neither restrictively mechanistic (bottom-up reductionism) nor wholly organismic (top-down holism). What kind of history of vitalism results from this new emphasis on the interrelation between mechanism and vitalism? I suggest that vitalism, at least when it is not caricaturally positing immaterial vital forces, is concerned with vital materiality overall, and particularly with 'the living machine', to borrow a phrase from Claude Bernard (Bernard 1865). 1. Mechanism and vitalism: the situation Mechanism and vitalism are very general terms but they convey equally vivid intuitions, that recur in different historical, theoretical and scientific contexts. Broadly speaking, mechanism