http://www.opus-bayern.de/uni-wuerzb...opus=122&la=de
This is a HUGE book on the history of PD and it is easy to read and it is free. Among the things you will find:
There have been a lot of other treatments before L-dopa and some seem to have worked as well.
Symptoms have changed considerably over the last 200 years.
Salvation has been just around the corner for an uncomfortably long time.