Previous communications have dealt with the antiseptic properties of compounds of the pyridine, quinoline, acridine and phenazine series, and also of the apocyanine, carbocyanine, and isocyanine groups, the object being to investigate relationships between chemical constitution and antiseptic properties. The following work comprises the preparation and examination of a large number of styryl and anil quinoline compounds, considerable variations in chemical structure being involved. The authors have previously drawn attention* to the possible influence of a particular chemical grouping consisting of a chain of alternate double linkages joining two nitrogen atoms, one being basic and trivalent, and the other the pentavalent nitrogen of a quaternary ammonium group. This arrangement is present in acriflavine (2.7 diamino acridine methochloride), and also in the cyanines, in all of which the antiseptic action is not diminished by the presence of serum. As shown by the graphic formulæ, the styryl compounds also include a similar system, whereas in the anils an additional nitrogen atom is interposed in the connecting chain in place of a —CH= group. This system will be subsequently described as the “ alternate linkage system.”

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that must depend upon the concentration of formalin in the tissues. I have used solutions of ammonia varying in density between 0'980 and 0'880, at 15" C., with equal success and without damaging the tissues. The cut sections are washed in distilled water and then placed in the ammonia solution for from 3 to 15 hours a t room temperature; then after thorough washing in distilled water (several changes), they are stained with carbol-fuchsine at 55" C. for two hours. They are then decolourised in the usual way and counter-stained with hsmalum.The method is evidently not perfected, but I publish this note as it might be useful to others more directly interested either in tubercle bacilli or in the removal of formalin from tissues. I