Which preposition to use with ergots

of Occurrences 2%

This is a subcutaneous glistening cord originating in the ergot of the fetlock, passing in an oblique direction downwards and forwards, and crossing over on its way both the digital artery and the posterior branch of the digital nerve.

in Occurrences 1%

in weight ten drops of the extract of ergot in a teaspoonful of water should be ample, given by the mouth.

Which preposition to use with  ergots