A vindication of a late Essay on the transmutation of blood, Containing The true Manner of Digestion of our Aliments, and the Aetiology: or, An Account of the Immediate Cause of Putrid Fevers or Agues. As also Observations upon the Noble Specifick Cortex Peruvianus. To which is Added, (by Way of Appendix) A Dissertation concerning the Manner of the Operation of Chalybeat Medicines in Human Bodies, in opposition to the receiv'd Opinion of their operating by their Pondus, &c. Founded upon experimental Observations and demonstrable Principles, the sole Original and Fundamental of true Knowledge, which our Senses are Witness to. By Thomas Knight, M. D