During the nineteenth century the analysis of urine was based on technical tools for the quantification of its constituents. The transformation of diagnostic signs into numbers made reference and normal values indispensable for the verification of the transition point between "normal" and "pathological". It needed the reconfiguration of disease concepts to link measured data and values with specific clinical pictures. Ontological disease concepts were replaced by a gradual understanding of health and disease. During this process the "normal value" became the crucial point of discussion.Taking a statement by Claude Bernard (1813-1878) about the nonsense of chemical mean values as a starting point the paper focuses on the contemporary debate about the role and function of quantification in medical diagnostics. The methodological reference points of the analysis are Georges Canguilhem's considerations about the normal and the pathological and Ludwik Fleck's thought collectives. The acceptance or rejection of normal value concepts is bound to specific thought styles. Permanent challenges to traditional qualifying semiotics resulted in a slow transformation of semiotic thought styles into quantifying diagnostics. The "technisation" of medicine during the nineteenth century fostered this process. The clinical laboratory helped to establish a"mathematisation" of medicine.