The evidence of the superior efficacy of the cinchona flava, or yellow peruvian bark : An essay, in which the correspondent preparations of the three peruvian barks most generally known are compared; and in which the yellow is proved to excel the pale and the red, by that evidence which is proper to materia medica. By Walter Vaughan, M.D. licentiate of the Royal College of physicians, London; physician at Rochester. To which is prefixed, a letter to the author, from Doctor William Saunders, F.R.S. and senior physician to Guy's Hospital.