One of the early ways by which man learns about the sur- rounding world is by taking to pieces an object which attracts his attention. This method, which is widely used by children, is re- sorted to once again by the adult who wishes to study natural phe- nomena. The method of dismantling a complete object into its parts so that it can be studied has found its widest and most suc- cessful application in biology and, in particular, in the study of living cells. The cytologist studying a cell will usually have to examine its fragments, which may be dead or semiliving. In sec- tions of killed...