“…The vaccine Bacillus of Calmette Guérin (BCG), used in the prevention of tuberculosis, was developed by two researchers, Albert Calmette and Camille Guérin, as an attempt to obtain homogeneous suspensions (without clumping) in the cultures of a very virulent bacillus, Mycobacterium bovis, isolated by Nocard from a heifer with mastitis in 1902 (Sakula 1983), in the Pasteur Institute of Paris. In the Pasteur Institute of Lille, Calmette, accidentally obtained a mutated organism, after passages in vitro of the sample of M. bovis by cultivating the cultures in potatoes impregnated in ox bile, and Guérin, his assistant, observed, after 231 passages in vitro of the sample of M. bovis, during 13 years, alterations in the morphology of the colonies and gradual loss of virulence.…”