Smallpox is an acute, specific, febrile, contagious disease preceded by an incubative period,
setting in suddenly with chills, headache, backache,
sweating, vomiting, and epigastric tenderness, and
characterised by the evolution of symptoms in a relatively determinate order, with a cutaneous efforescence successively papular, vesicular, and pustular in
type, followed by cresting, and terminating either
fatally or by complete convalescence, with or without
sequelae in the form of multiple, circumscribed, and . superficial cicatrices; one attack, as a rule, exausts or destroys the susceptibility to the disease,
in the same person for the remainder of life.