348 Veranus Alva Moore 



mordant which contains tannic acid. The other elements 

 have varied. The technique of the method therefore consists 

 in treating the cover glass preparations of the bacteria with a 

 mordant prior to, or together* with, the application of the 

 staining fluid. 

 The mordant rj" 



A 20 per cent, solution of tannic acid 10 cc. 



A cold saturated solution of sulphate of iron 5 cc. 



A saturated alcoholic solution of fuchsin i cc. 



If possible chemically pure tannic acid should be used. 

 This mordant can be used in staining the flagella of these 

 three species of bacteria, but slightly better results appear to 

 be obtained with the typhoid and colon bacteria when a few 

 drops of a 10 per cent, solution of sulphuric or acetic acid are 

 added. With the hog cholera bacteria a mordant containing 

 a 10 per cent, solution of tannic acid gave equallj' good results. 



The staining fluid. ■% For this I have used carbol fuchsin 

 prepared after Ziehl's formula. 



*I have found, since the greater part of the work on this article was 

 completed, that certain staining fluids (alcoholic solutions) could be 

 mixed with themordant thus eliminating their subsequent application. I 

 have not perfected the formula for this combination but have obtained 

 excellent results -with a fluid composed of a 20 per cent, solution of 

 tannic acid 2 cc, saturated solution of sulphate of iron i cc, and a sat- 

 urated alcoholic solution of fuchsin i cc, filter and applj' in the same 

 manner as the mordant, but for a much longer time. 



tThis is Loeifler's standard or neutral mordant. It is successful!}' 

 employed in staining the flagella on many motile bacteria. The 

 addition of a few drops of a 10 per cent, solution of sulphuric acid era 

 similar quantity of a i per cent, solution of sodium hydrate appears to 

 give better results, if indeed it is not absolutelj- necessary, with certain 

 other species. My personal experience tends to prove that no sharp 

 and fixed lines can be determined for the preparation of a universal 

 mordant. I have been unable, however, to stain a single flagellum by 

 the use of a mordant not containing tannic acid, although I have tried 

 nearly all of the known " fi.xatives." As I have stated elsewhere'^ a 

 weaker solution of tannic acid can sometimes be used with advantage. 



X I have stained the flagella with nearlj' all of the basic aniline Ayes 

 ordinarily used in bacteriological work. The carbol fuchsin gives a 

 deeper stain and consequently a clearer definition of the filaments is 

 obtained. 



