An Analysis of Photoelectric Instruments for Measurement of Turbidity with Reference to Serology

Abstract

One method for determining the systematic position of animals is to measure the amt. of precipitate formed in the reaction of an autiserum with its homologous antigen and to compare it with the amt. of precipitate obtained in the reaction of the same antiserum against heterol-ogous antigens. This precipitate can be measured by several methods: (1) direct volume measurement, (2) nephelo-metric measurement of the light scattered by the particles in suspension, and (3) the measurement of precipitate by densi-tometry on the basis of the Bouguer-Beer law applied to turbid systems. Recent work tends toward the use of the more rapid techniques employing photo-electric instruments in nephelometry and densitometry. Before extensive use is made of these instruments it is essential that the reliability and limitations of the instruments and techniques be checked". The exptl. data obtained for this paper, using suspensions of known precipitate conc. to simulate serological conditions, illustrate that a linear relationship exists between conc. and instrument reading for a wide degree of precipitate formation in densitometry but the great sensitivity of nephelometric techniques limits its use to lower concs. of precipitate. From these studies, procedures in serology are suggested showing their use in an actual relationship study. Using these proposed procedures, the relationship data obtained from an anti-serum reacted against both homologous and heterologous antigens are essentially the same regardless of the 3 methods of precipitate measurement employed.