Sentence:  But Hairs make fallible Predictions, and many Temples early gray have out-lived the Psalmist's Period. Hairs which have most amused me have not been in the Face or Head, but on the Back, and not in Men but Children, as I long ago observed in that Endemial Distemper of little Children in Languedock, called the <WSD>Morgellons</WSD>, wherein they critically break out with harsh Hairs on their Backs, which takes off the Unquiet Symptomes of the Disease, and delivers them from Coughs and Convulsions. 
Meaning of the word marked with <WSD> tags:  A disease causing hairs to grow on the backs of children.