Many standard textbooks of physiology have a diagram that shows the transporting elements that lead to the secretion of HCl by the parietal cell. The transporters are neatly aligned, and students see an elegant mechanism that neatly balances the ions to maintain electroneutrality. They little realize the time and effort required to tease out each of those steps bit by bit. This essay uses three papers by Horace Davenport to highlight the experimental evidence for a crucial step in that process: the generation of H+ and HCO3− through the agency of carbonic anhydrase. All three papers form part of the classic papers available through the American Physiological Society Legacy Project.