Stephen Hales: the contributions of an Enlightenment physiologist to the study of the kidney in health and disease.

Stephen Hales (1677-1761) was an English clergyman who made major contributions to a wide range of scientific topics such as botany, chemistry, pneumatics, and physiology. Early in his career he developed a keen interest in medicine through his association with his younger physician friend at Cambridge, William Stukeley (1687-1765), with whom he dissected animals and attended experiments in the laboratory of Isaac Newton. His fame as a scientist grew and by the end of his life he had achieved an international reputation as a major scientist of the Enlightenment. He is best known for his 1733 Statical Essays, in the second part of which he describes his studies in animal physiology. Most famous amongst those are his assessments of the force of the blood, which he measured in horses and dogs. Less well known and often unrecognized are his studies on the kidney in health and disease, which are the focus of this review. Amongst others Hales described the effects of hemorrhagic shock which he observed as he bled his animals while measuring their blood pressure; he then studied the effect of increasing saline perfusion pressures on the renal secretion of urine; and delved into biochemistry in exploring the composition of and solutions to dissolve bladder stones. His 1733 statement in the introduction to his hemodynamic studies that the healthy State of the Animal principally consists, in the maintaining of a due Equilibrium between the body solids and fluids literally predicts the milieu intrieur that would ultimately be formulated in 1854 by Claude Bernard (1813-1878).