Injecting a horse with diphtheria toxin, New York City Health Department, 1940s

Courtesy Library of Congress

Large animals like horses were essential to produce the quantities of serum needed to supply the population.

Man in a lab coat injecting a horse in the neck.

Bleeding a horse for antitoxin production, 1940s, New York City Health Department, 1940s

Courtesy National Museum of American History

Man in a white jumpsuit holds a piece of rubber tubing to a horse’s neck to drain blood. Woman in a white lab coat holds canister to collect draining blood. Another man stands in the background.

Collecting blood from horses for antitoxin production, Parke, Davis & Company, ca. 1925

Courtesy National Museum of American History

Two men in white suits and caps stands next to two horses secured in metal stalls. The men hold long glass canisters to collect blood draining from tubing attached to the horses’ necks.

Injecting a horse with diphtheria toxin, Parke, Davis & Company, ca. 1925

Courtesy National Museum of American History

A man in white coat injects toxin into the neck of a horse held in a metal stall.