3. They do not stand decolorization quite as well as the tubercle bacillus. With 20% sulphuric acid in water they hold their color almost as well as tubercle bacilli but with 3% HCl in alcohol they decolorize in about two hours as against twelve to twenty-four hours for the tubercle bacillus.
4. Leprosy bacilli have neither been surely cultivated nor surely inoculated with pathogenic results into guinea pigs or other experimental animals and it is by the negative results upon cultivating or animal inoculation that we have our surest method of differentiation from tubercle bacilli.
Leprosy bacilli are chiefly spread through the lymphatics, but in nodular leprosy, their occurrence in the blood stream during the febrile accessions is so constant that this route may also be of importance. Next to the corium they are most abundant in the lymphatic glands. They stain readily by Gram’s method.
A great amount of work has been done within recent years in attempting to cultivate the leprosy bacillus.
In 1900 Kedrowsky culturing material from 3 cases of leprosy obtained diphtheroids from two and a streptothrix from one. A rabbit was inoculated first intracerebrally and later intraperitoneally with this nonacid-fast streptothrix and, when killed six months later, showed peritoneal nodules, from which both diphtheroids and acid-fast bacilli, but not a streptothrix, were recovered culturally. Injections of cultures of the acid-fast bacilli and diphtheroids into rabbits and mice produced nodules which when cultured showed acid-fast organisms or diphtheroids.
In 1901 he cultivated a diphtheroid from a fourth case of leprosy.
Fraser and Fletcher working with Kedrowsky’s culture produced peritoneal nodules with the killed as well as the living organism. They were able to produce the same results with B. phlei. With emulsions of leprous nodules, rich in leprosy bacilli, they could not produce similar lesions in the experimental guinea pigs.
Rost obtained a culture on a salt-free medium from which he prepared his leprolin by a process similar to that used for old tuberculin. It was claimed that leprolin had marked curative power in leprosy. Recently Williams and Rost have cultivated a streptothrix on a medium containing milk.
Clegg, by inoculating his medium with cultural amoebae, obtained growth of a diphtheroid organism, with acid-fast tendencies, from the spleen pulp of lepers.