A letter from J. Keyser, [electronic resource] : surgeon and chymist, of Paris, to Mr. Jonathan Wathen, surgeon, of London, In answer to his Pamphlet, intitled, Practical Observations on the Venereal Disease, &c. in Which he has introduced and espoused certain Animadversions of an anonymous Writer on the celebrated Medicine called Keyser's Pills. To which is added, a letter from the learned Professor Le Cat, of Rouen, with an Account of a remarkable Cure that Gentleman performed with this Medicine.