MICROSCOPICAL EXAMDFATTOV Of BACTERIA. 91 



held over the flame until steam rises. The mordant is then washed 

 off with distilled water, and all traces removed from the edge of 

 the cover-glass with alcohoL The stain is filtered, and a few drops 

 allowed to fall on the film, and after a few minutes the cover- 

 very carefully warmed until steam rises. The stain 

 off with distilled water, and is ready to be examined and 

 subsequently mounted. For some bacteria it is necessary to modify 

 the solutions, either by the addition of acetic or sulphuric acid, or 

 by varying the quantity of soda solution. 



L introduced a modification of Lofflers system. Cover- 

 are floated for from two to twelve hours on a solution 

 of 1 per cent, tannin and | per cent, hydrochloric acid. 

 After washing in water the preparation is stained with a saturated 

 alcoholic solution of any of the amtine dyes diluted in the propor- 

 tion of 2 drops of the dye to 20 of water. The cover-glasses 

 in the solution for from two to four hours are then 

 in water, and examined. The best results are obtained with 

 carbofised fnchsine, diluted in the proportion of 2 drops to 20 drops 

 of 1 per cent, carbolic. Trenkmann also recommended the use of 

 catechu and logwood as mordants, with the addition of very dilute 

 acid, and subsequent taimtg with fnchsine. 



Lutesch suggested the use of ferric acetate. To avoid any 

 deposit on the surface of the preparation, freshly prepared saturated 

 ferric acetate is used, and 5 to 10 drops of acetic add are added to 

 16 ce. of the mordant. After warming the solution the preparation 

 is washed in water, followed by 20 per cent, acetic acid, 



gentian-violet in aniling* water. 



Tan Ermengem used a mordant composed of 1 part of 

 2 per cent, solution of osmie acid, 2 parts of 10 to 25 per cent, 

 solution of tannin, with to cvtsj^ 100 ce. of this mixture 4 or 5 drops 

 of acetic acid. A black ink is thus formed, and the solution is 

 applied for from five to thirty minutes. After washing in water and 

 alcohol the cover-glasses are placed in a solution of nitrate of silver 

 and transferred to another solution composed of 5 grammes of gallic 

 acid, 3 grammes of tannin, 10 grammes of acetate of soda, and 330 

 grammes of distilled water. In a few moments they are again placed 

 in nitrate of silver, and then washed and mounted in balsam. 



oCuLVO i> tPf^MlOd AOSWCsTS ^ndl lOB* CCB^tstMTl HI if sffEmffP|W ^IflffBttfv AO<6? 



preparations are left for one minute in solution of tannin, washed in 

 dirtilipd water, transferred for a minute to 50 per cent, phospho- 

 molybdic acid, again washed and stained from three to five 



