material aspects of a living system are the struts and levers of a machine

An example of the use of metaphor in scientific writing,

"The new interest in the physical nature of biological systems has coincided necessarily with the development of new physical tools, theoretical and practical. Of the former, by far the most important is the development of the quantum theory and its extension to cover at least in principle the theories of chemistry and to give precious indications of the far more complex phenomena of biochemistry and biophysics. Without exaggeration it can be said that the conception of quantum energy changes in chemical reactions is the most illuminating most effective new idea in modern biology. We begin to see now that the material aspects of a living system are but the struts and levers of a machine, the particular function of which is to effect energy interchanges, and that growth and assimilation are but means of achieving a metabolism consisting of enzyme promoted energy changes. Thus in a very physical sense process takes precedence over structure."

J. D. Bernal (1951) The Physical Basis of Life, Routledge and Kegan Paul

The idea of the organism as a machine was not new with Bernal (for example, Descartes saw animals as automata, and humans as machines that also had a soul.)