Experimental Systems - continued

A particular feature of experimental systems in the life sciences is that in one way or the other they are tied to the use of model organisms. It appears to be a peculiar characteristic of living beings that the differences they show among themselves are shaped by deep historical, evolutionary contingency. Yet the modern biologist also assumes that there are underlying commonalities between different organisms which, once developed, have been conserved throughout evolution. They represent more or less wide-ranging metabolic or developmental mechanisms up for description in terms of cellular and molecular structure and function. This situation leaves the biologist with two problems. The first is that it will basically be a matter of inductive generalization to decide how ubiquitous a particular character of living beings turns out to be. There are no a priori reasons for biological generalities. The second problem that the biologist will have to make choices: A particular character may be more accessible, more easily discerned and determined in its general features in one specific class of organism than in another. It is in this context that model organisms have started to play an increasing role in the second half of the nineteenth century in physiology, and at the beginning of the twentieth century, in research on heredity, cytology, and embryology. Here, model organisms are thus ‘ideal’ objects, first, in that they represent a particular phenomenon in an easily accessible fashion, and second, in that they can be handled in a productive operational way in the process of setting up an experimental system. This last point appears to be particularly important: In order to function as model organisms, they need to be embedded in experimental systems, where they can play out their dynamics and function as exemplars. Their entrenchment in experimental systems may even make them, at least to a certain degree, resistant against being replaced by potential competitors in a particular historical window of time. Model organisms entrenched in experimental systems can, to speak with Gaston Bachelard, turn into “epistemological obstacles” (Bachelard 1969). Idealization may go so far as to have material consequences, that is, to materially change the model organism under investigation, e.g., the creation of pure lines or of particular gene combinations in genetic model organisms. Drosophila serves as a good example here (Kohler 1994). Model organisms are thus, as a rule, also organisms modified for particular research purposes.