Sentence:  If the predisposition to the disease has arisen from a plethoric state of the system, or from a turgescence in the vessels of the head, this is to be <WSD>obviated</WSD> by bleeding, both generally and topically, but more particularly the latter; an abstemious diet and proper exercise; and by a seton in the neck. 
Meaning of the word marked with <WSD> tags:  To avoid (a future problem or difficult situation).