26 [ AGAR ELECTROPHORESE-DENSITOMETER FOR ELECTROPHORESIS; PHOTOMETERS, COLORIMETERS, HEMOGLOBIN PHOTOMETERS, INTEGRATING LINEAR AND LOGARITHMIC RECORDERS, LINEAR AND LOGARITHMIC ANALOGUE TO DIGITAL CONVERTERS, ] INSTRUMENTS FOR MEASURING PHYSICAL VARIABLES AND INSTRUMENTS FOR CALCULATION OF SUCH VARIABLES, AND INSTRUMENTS FOR INDICATING, RECORDING OR TABULATING THE OBTAINED INFORMATION OR COMBINING THIS INFORMATION