The logistic curve for the fitting of sigmoidal data.

In 1838 a differential equation was developed by Verhulst to explain what is currently termed the S-shaped curve. Reviewed here are his application of the equation to population data and significant later applications by various workers to problems in physics, chemistry, and biology. The usefulness, versatility, and convenience of this integrated equation are illustrated by examples from our own work, including superimposition of data by use of reduced variables.