One can also program the computer to “erase” one or more nodes and its connections in the network. By making the assumption that any papers which derive from these nodes should also be erased, one can then determine whether an alternate “critical path” to a subsequent discovery does exist. Thus, one can legitimately ask whether the work of Whitnah on the physical properties of milk22 or Elworthy ’s work on lecithin micelles23 would have been possible if Einstein had not published his paper on measuring dimensions of molecules! 24 Further, by counting the totaJ number of “terminal” nodes erased, onc may possibly obtain a useful quantitative measure of historical impact. A terminal node is a member of a particular set of papers, as, e.g., all 1962 papers. The critical impact of Einstein’ s work would be the percentage of 1962 papes which, one assumes, would not have been written if they could not have cited either Einstein’s papers or papers which have cited Einstein. In making such calculations, one has to also consider the papers cited by Einstein.