46 MICRO-ORGANISMS IN WATER 



and ready for use. This solution does not keep its 

 staining power for more than from fourteen days to one 

 month. 



The above solution has been modified by Loffler 

 and its tinctorial power greatly increased by dissolving 

 5 grms. of solid fuchsine or any other basic colour in 

 100 c.c. of c aniline water ' prepared as above. It will 

 retain its tinctorial powers for from four to six weeks, and 

 is best preserved in a tightly stoppered bottle in a dark 

 cupboard. The intensity of the stain may be still 

 further increased by adding a solution (1: 1,000) of 

 caustic soda drop by drop, until the previously clear 

 coloured liquid just begins to become clouded and 

 before any actual precipitation takes place. This latter 

 modification renders the solution less permanent in its 

 staining properties. In applying this it is best to filter 

 a few drops direct on to the cover-glass preparation 

 which is to be stained. 



Another modification of Ehrlich's solution is that 

 introduced by Weigert and Koch. To 100 c.c. of the 

 aniline water add 11 c.c. of a concentrated alcoholic 

 solution of fuchsine or methyl violet and 10 c.c. of 

 absolute alcohol. This solution will keep for from ten 

 to twelve days. 



Zielifs solution. The principle of this is precisely 

 the same as that of the ' aniline water ' solutions just 

 described, the aniline being replaced by the oily sub- 

 stance, carbolic acid. It may be most conveniently 

 thus prepared: 5 grms. of carbolic acid and 1 grm. 

 of fuchsine are added to 100 c.c. of water to which 

 10 c.c. of alcohol is gradually added. The advantage of 

 this solution is its greater permanence over that of 

 Ehrlich's, although its tinctorial power is not quite so 

 great. Klilme has replaced the fuchsine by adding 1--5 

 grm. of methylene blue to 10 c.c. of alcohol, which is 



