The bacillus of Hansen is a mycobacterium that belongs to the Mycobateriaceae family, to the Actinomycetales order to the Schizomycetes classroom. The Mycobacterium leprae or bacillus of Hansen has form of linear rod or lightly incurvated, to the times in form of clava or rod of drum or, still, in form of bar bells; the length varies enters 1,5 the 8 m and the 0,2 width enters 0,4m and however it is multiplied each the 14 20 days in the laboratory animal, is admitted from there that the time of multiplication in the man is longer, the characteristic of its slow evolution and insidiosa who elapses the disease, divides itself for binary fisso, is one gram positive and strong alcohol-acid-resistant (FOCACIA, 2005) it is classified as being an obligator intracellular parasite that inhabits in fagolisossomas of the macrophages and in vacolos of cells endoteliais and of cells of Schwann of nerves peripheral, and this analogy can to be explained for comment of that the Mycobacterium Leprae possesss the power of is leagued expecificamente to the extracellular components of the surface of the cell of Schwann, that takes the internalizao of the bacillus, is considered as a mycobacterium that contains cidomiclico, arabinogalactan and phenolic glicolipidio in cellular wall (GOLDMAN; AUSIELLO, 2005). In agreement the clinical forms the Hansenase or Mal de Hansen is an infectious illness of aspect caused by the Mycobacterium leprae, that it has discontinous chronic course for reacionais surtos, affecting the peripheral skin and nerves. The natural reservoir of the bacillus is admitted to be the man, even so has stories of natural infection in animals as armadillos, monkeys and chimpanzees. I infect it occurs of individual for individual, being the ways of elimination and entrance of the bacilli injured parts of the skin or mucosae and aerial ways injured of the skin or mucosae and ways aerial superiors.