18 THE AMEEICAN MONTHLY [Januaiy, 



obtained with dahlia, fuchsin, or methyl violet. The most desirable stain is car- 

 bol fuchsin (2 drops of a concentrated alcoholic solution of fuchsin to 20 drops 

 of a I per cent, solution of carbolic acid). 



In a second process recommended in the same article catechu was employed. 

 An excess of powdered catechu was placed in water and allowed to macerate for 

 several days and filtered. The filtrate impregnates the flagella somewhat feebly 

 without the addition of an acid. The cover-glass preparations, prepared as above, 

 are placed in a solution composed of four parts of the filtrate and one part of a 5 

 per cent, solution of carbolic acid. They are allowed to i-emain in this for from 

 2 to 12 hours, after which they are stained in the same manner as by the first 

 process. 



A third process is recommended, which consists in placing the cover-glass 

 preparations in a concentrated solution of logwood for from 2 to 12 hours, after 

 which they are washed and stained in some of the aniline dyes. Fuchsin is 

 especially recommended. The addition of an acid is said to improve the mordant 

 properties of the logwood solution. The acids proposed are hydrochloric (i per 

 cent.), gallic (7 per cent.), or carbolic (i to 2 per cent.). 



Trenkmann also obtained positive, though less satisfactory results, by three 

 other methods of procedure, (i) The preparations are transferred from the 

 solution of the extract of logwood to Bohmer's or Grenadier's htematoxylin solu- 

 tion. (2) The specimens are first treated in gallic acid and then stained with 

 some of the aniline dyes. (3) The preparations are treated first with h<ema- 

 toxylin solution and then with an aniline dye. 



By the use of these methods he was able to demonstrate the tufts of 

 flagella on many spirilla, especially the spirillutn undula and a water 

 bacillus. 



Loeffler's Method. H. — About one year after the publication of his 

 first method, Loefiler announced (7) a second process for the staining 

 of flagella which is a marked improvement over the procedure first 

 recommended. In his careful investigation into this subject he suc- 

 ceeded in discovering an important principle by the observance of which 

 it is supposed that the flagella on all motile bacteria can be stained. 

 This cotisists in the degree of acidity or alkaliitity of the mordant. 

 In applying this principle he found that those germs which were acid- 

 producing organisms (those that will change an alkaline medium to an 

 acid one during their development) , such as the typhoid bacillus and 

 others, require an alkaline mordant, and that the alkaline-producing or- 

 ganisms (those that convert an acid into an alkaline medium during their 

 development), such for example as the cojuma bacillus., the spirillum 

 of Finkler-Prior, the bacillus of blue milk and others, require an acid 

 mordant. The degree of acidity or alkalinity of the mordant necessary 

 to secure the staining of the flagella of a specified germ must be deter- 

 mined by actual experiment ; when this is accomplished the method 

 does not differ materially from that first proposed. The formulte for 

 the preparation of the mordant and staining fluid, together with the 

 details in their application, are as follows : 



(i) The Mordant. — To 10 c.c. of a 20 per cent, aqueous solution of tannin 5 

 c.c. of a cold saturated solution of the sulphate of iron and i c.c. of an aqueous 

 or alcoholic solution of fuchsin, methyl violet, or " Wollschwarzlosung" are 

 added. The fuchsin is especially recommended. 



The foregoing solution is to be regarded as the standard or stock solution to 

 be used, and one which is successfully employed in staining the flagella of cer- 

 tain micro-organisms; but for others the addition of an acid or alkali is neces- 

 sary. Thus for the comma bacillus it is necessary to add to the 16 c.c. of mor- 

 dant ^ to I drop of a solution of sulphuric acid equivalent to a i per cent, solu- 

 tion of sodium hydrate; for the spirillum rubrum 9 drops of the acid solution 

 are required. For the typhoid bacillus i c.c. of a i per cent, solution of sodium 



