Sentence:  No dangerous diseases almost whatsoever, are more successfully <WSD>oppugnable</WSD> under discreet medical regimen [than are the fevers hitherto described] ; and when entrusted to nature, from the days of Hippocrates to the present time, they have ever been extremely fatal. 
Meaning of the word marked with <WSD> tags:  (rare) Curable, amenable to medical treatment.