Sentence:  This is likewise evident in such as walk in the night in their sleep, and do strange feats: these vapours move the phantasy, the phantasy the appetite, which moving the <WSD>animal spirits</WSD> causeth the body to walk up and down as if they were awake. 
Meaning of the word marked with <WSD> tags:  The theorized ‘spirits' or physiological principles which allowed for sensation and voluntary movement. (from 15th c.)