In addition to this new or second-degree relativity of interior and exterior, there is a whole history on the level of the membrane or limit. To the extent that elements and compounds incorporate or appropriate materials, the corresponding organisms are forced to turn to other "more foreign and less convenient" Materials that they take from still intact masses or other organisms. The milieu assumes a third figure here: It is no longer an interior or exterior, milieu, Even a relative one, nor an intermediate milieu, but instead, an annexed or associated milieu. Associated millieus imply sources of energy different from ailmentary materials... Obtaining an energy source permits an increase in the number of materials that can be transformed into elements and compounds. The associated milieu is thus defined by the capture of energy sources (respiration in the most general sense), by the discernment of materials, the sensing of their presence or absence (perception), and by the fabrication or non-fabrication of the corresponding compounds (response, reaction). - Deleuze and Guattari, A Thousand Plateaus, 10,000 B.C.: The Geology of Morals (Who Does the Earth Think It Is?)