cell theory: (biology) the theory that cells form the fundamental structural and functional units of all living organisms; proposed in 1838 by Matthias Schleiden and by Theodor Schwann
scientific theory: a theory that explains scientific observations
fornix: an arched bundle of white fibers at the base of the brain by which the hippocampus of each hemisphere projects to the contralateral hippocampus and to the thalamus and mamillary bodies