Whiteside described a reaction between sodium hydroxide and milk that resulted in the thickening of mastitic milk. The utility of this reaction as a field test was limited by the fact that the reaction was sometimes difficult to observe, and would eventually occur even in normal milk. A refined version of the test, which enhanced its sensitivity, and eliminated the confounding effect of milk fat, uses an anionic surfactant, which forms a gel with the DNA in somatic cells in the milk