Every therapeutic measure of value necessarily passes through three stages: evolution, standardization and evaluation. It is discovered or evolved; is used, and by usage becomes definitely formulated; and finally the results obtained, especially the permanent or end-results, are studied and interpreted.
While these periods are not always chronologically distinct, nor always of equal importance, they can be definitely traced in the history of every method of treatment that has passed the twin sentinels of time and trial.
It often happens that methods of therapy have an immediate beneficial influence, even a startling success, but in many cases a follow-up of these seeming cures has shown that the successes are not as uniform as the immediate effect indicated. For this reason, and others which will readily occur, systematic investigation of end-results is desired in any therapeutic measure that has elements of success in it, or that has been fairly well standardized.