Types. Economists Ronald G. Ehrenberg and Robert Smith, authors of Modern Labor Economics, identify two main types of labor unions: craft unions and industrial unions. Craft unions represent workers in a specific occupation.lthough union membership in the United States peaked in the mid-20th century and has declined since then, various types of labor unions remain an influential force in American business and politics.
U.S. Army Physicians Discovered the Cause of Yellow Fever. August 27, 1900. No one knew what caused the often-deadly yellow fever, but it occurred in epidemic proportions, with one person after another in a given area becoming sick. People feared the mysterious disease, until U.S. Army physician James Carroll endangered his own health in the name of science.
From Conservapedia. The Germ theory of disease, developed in the 1860s and 1870s by Louis Pasteur, states that tiny living beings are the cause of infectious diseases. The theory was developed to explain puerperal fever, or Child bed fever.nly after the germ theory was championed by Pasteur (see pasteurization) and Lister (namesake of Listerine mouthwash) did antiseptic medicine become popular. Prior to germ theory, it was widely believed that disease was spread by noxious odors.