Which preposition to use with practicers

of Occurrences 1%

Helmont disguised; or the vulgar errors of imperical and unskilful practicers of Physick confuted; more especially as they concern the cures of Feavers, the Stone, the Plague, and some other Diseases by way of Dialogue; in which the chief rarities of Physick are admirably discoursed by I.T. Books in the Press, and ready for Printing.

Which preposition to use with  practicers