TEXT-BOOK OF BACTERIOLOGY. 45 



better to stop short of saturation, and stain for a longer time with 

 a thinner solution. Phenol, or oxybenzol, is nearly related to an- 

 ilin, or amido-benzol, and is employed in like manner. Thus in 

 Ziehl's solution we have a combination of aqueous carbolic acid and 

 fuchsin. 



Ziehl's Solution. 



Aqua destil., 100 grams. 



Acid carbolic cryst., 5 " 



Alcohol, 10 " 



Fuchsin, 1 gram. 



This can be made very easily by taking a 5 per cent aqueous 

 solution of carbolic acid and adding concentrated alcoholic solution 

 of fuchsin till saturation is reached. In the same manner we pre- 

 pare a mixture of methyl-blue and phenol, as recommended by H. 

 Kiihne. Put 1 to 3 parts of coloring matter into 10 to 15 parts of 

 pure alcohol — that is, make a concentrated solution — and add this 

 in suitable quantity to about 100 cm. of 5 per cent carbolic acid so- 

 lution. 



We have still to mention the combination of anilin stains with 

 potash. Methyl-blue in particular, which, though it has but slight 

 coloring power, nevertheless j-ields beautiful and distinct pictures, 

 gains by this mixture a considerablj'^ extended field of usefulness 

 and an almost unlimited power of staining all kinds of bacteria. 

 Two solutions of methyl-blue and potash are particularlj' useful; 

 the one called Koch's solution, or the weak solution, con.sists of: 



Concentrated alcoholic sol. of methyl-blue, . 1 gram. 



Distilled water, 200 grams. 



10-per-cent solution of liquor potassEe, . . 0.2 gram. 



The other — LoflBer's, or the strong solution — consists of: 



Concent, alcoholic sol. methj'1-blue, ... 30 grams. 

 Liquor potassse 1 : 10,000 (0.01 per cent), . . 100 " 



The latter especially is a really excellent stain, which hardly 

 ever proves refractory. 



Carbonate of ammonium in 0.5 to 1^ solution, as recommended 

 by H. Kiihne, acts in the same manner as the potash. It is, how- 

 ever, not applied together with the coloring matter, but serves as a 

 sort of preliminary mordant. The preparations are placed in it for 

 a few moments before being transferred to the staining solution. It 

 Is a combination of two such proceedings which Loffler has recently 

 recommended for the staining of bacterial preparations in general. 



