The Collaborative International Dictionary of English v.0.48:

Organicism \Or*gan"i*cism\, n. (Med.)
   The doctrine of the localization of disease, or which refers
   it always to a material lesion of an organ. --Dunglison.
   [1913 Webster]

WordNet (r) 3.0 (2006):

organicism
    n 1: theory that the total organization of an organism rather
         than the functioning of individual organs is the
         determinant of life processes