Sentence:  ... there be three things, and every one full of under-branches belonging to this "Art" and way of "Healing:" The first is knowledge of the "Diseases:" the second is the "Remedies" against them: and the third of the <WSD>"appliance</WSD>" of "Remedies;" All which should be traversed in this Discourse. 
Meaning of the word marked with <WSD> tags:  The act of applying.