The chemotherapeutic action of compounds of bismuth in spirochaetal infections was observed by Robert and Sauton. These workers found that sodium bismuthyl tartrate had a marked effect in preventing and curing infection with Spirochaeta gallinarum (Fowl Spirillosis). Since then the action of compounds of bismuth has been extensively investigated in spirochaetal infections (see Levaditi). The present work concerns the bismuth derivatives of organic hydroxy-acids. All the compounds investigated are white amorphous solids, of which only the derivatives of the monobasic sugar acids are at all soluble in water. They are stable to acetic acid, but are instantly decomposed by dilute mineral acids; and; with the exception of the citric acid and ester compounds, are soluble in alkali. The therapeutic action of these compounds was tested in the case of mice infected with Sp. laverani (Breinl and Kinghorn; Sp. muris of Wenyon). Infections with the strain used, which was non-pathogenic for mice, had the following characteristics:—As a rule, five or six days after subcutaneous in oculation with a suspension in saline of infected blood, the organisms were found in the peripheral circulation in small numbers. Thereafter they usually became more numerous and persisted for long periods. Their abundance in the blood appeared to vary from time to time and after some months they might become very scanty. The value of this infection as a test for chemotherapeutic properties lies in the fact that it is susceptible to agents such as salvarsan, which are effective in the treatment of infections with Tr. pallidum .