The successful treatment of the various diseases which afflict mankind is based upon sound conception of pathology, while pathology has for its basis an absolutely correct knowledge of physiology. In the formation of pathology, physiology is indispensable. In order to reach a correct diagnosis we must have a correct system of pathology. Were the physiological conditions and principles always clearly known and understood, our system of pathology might approach perfection, but physiology is not an exact science, perhaps never will be. Absolute knowledge in regard to all and every physiological state and condition may never be attained. Physiology may be said to be one of the least mature, because one of the most complex of the sciences. Therefore our pathology may remain defective, and if so, the practice of medicine will continue to be an imperfect art, medicine will continue to be a progressive but not an exact science.