The "jerks": mass hysteria or epilepsy?

Hysterical "epidemics" of "epilepsy" are well known in Eastern and Western cultures. A unique situation in the United States in the 19th and 20th centuries was the American religious movement, the setting in which "the jerks" occurred. Descriptions of various types of "jerks," including dancing, barking, laughing exercise, running exercise, and singing exercise are described.