That these Epidemics ceased was due to the discovery that by infecting the body with a mild form of the disease, it could be made to develop substances which render it immune to the deadly form.
"The Book of Life: Vol. I Mind and Body; Vol. II Love and Society"
Upton Sinclair
A great many Epidemics of typhoid fever occurred in just this way, before people realized how great this danger was.
"A Handbook of Health"
Woods Hutchinson
A modern city must know who is accountable when an automobile runs over a pedestrian, when a train load of passengers lose their lives because of an engineer's carelessness, when an employee is incapacitated for work by an accident for which he is not responsible, or when fever Epidemics threaten life and liberty without check.
"Civics and Health"
William H. Allen