114 THE CAUSATION OF DISEASE. 



The evolutions of which we are speaking are, for the most 

 part, partial ; but a partial evolution is, in some sense, the 

 equivalent of incomplete dissolution, and, in either case, a 

 tissue state is produced which is tinged, more or less, with 

 ancestral characters. In so far, then, as all diseases accom- 

 panied by distinct structural change are undoubtedly examples 

 of either partial dissolution or of partial evolution, they may be 

 regarded as local reversions. 



Here, however, we have to ask the important question — Are 

 these reversions true ? Does the affected tissue take on exactly 

 all the characters of some remotely ancestral tissue ? It may, I 

 think, be asserted a priori that this cannot happen in all cases. 

 In healthy granulation-tissue, we have an example of more or 

 less perfect reversion; but here, be it noted, the cell E is 

 healthy. In all cases of partial dissolution and evolution the 

 cell E is unhealthy. The elements of the tissues are subjected 

 to a species of mal-E unlike any which they have experienced 

 during the long course of their ancestral life. Now, we have 

 seen that E is capable of modifying S, and from this it is 

 obvious that a perfect reversion is quite impossible under a 

 mal-E ; for, even supposing, for the sake of argument, such 

 perfect reversion to occur, the altered E would necessarily 

 cause some modification in the truly reverted character. It 

 therefore happens that, in almost all cases of local reversion 

 occurring in disease, the evolutionary or dissolutionary process 

 is not only incomplete, but erratic. Wherefore it is more 

 accurate to style these reversions " local vitiated reversions." 



