The most elegant immunological experiment of the XIX century

When we remember that immunology was barely a decade old and knowledge of circulating antibodies only two years old when Ehrlich performed the experiments described, we can appreciate the inventiveness of his experimental designs. With little wasted effort he planned simple and rapid experiments to answer crucial questions about the mechanism of passive transfer of antibody from mother to fetus to suckling young. Most remarkable and difficult were the foster mother experiments, as anyone who has tried these with mice will attest. But they were judged to be critical and thus were pursued with ultimate success. These experiments would not be improved upon for 60 years, when the identification of immunoglobulin classes made differential transplacental and transglandular passage of immunoglobulins an object of interest. To conceive of studying the kinetics of the immune response by measuring changes in antibody concentration in the milk of lactating animals was yet another demonstration of the fertile imagination that had contributed so much to histology and hematology, and would soon contribute equally to experimental oncology and to scientific pharmacology.