Lustgarten has described a bacillus whose connection with syphilis still stands in need of proof. He has found it in the secretions and in the tissues affected with syphilis. It is a rod lomewhat resembling the tubercle bacillus, and is always found inside cells. It presents peculiar relations to staining agents, requiring treatment with gentian-violet, permanganate of potassium, and sulphuric-acid.

Giacomi ("Correspondenzbl. f. schweiz. Aerzte," 1885) describes a simpler method. A cover-glass preparation or section is placed for a few minutes in a heated aniline water fuchsine solution, afterwards washed in water containing a few drops of chloride of iron, and then decolorized in a concentrated solution of chloride of iron. The bacilli remain red, while all other bacteria are decolorized.

The position of this bacillus is doubtful, on the one hand because it is not found constantly in syphilitic lesions, and on the other because a similar bacillus has been found in the normal preputial and vulvar smegma.