56 MICEO-ORGANISMS IN WATER 



exact manner in which the whole process is carried out 

 is as follows : 



The cover-glasses must be perfectly clean, and 

 especially free from all grease (see p. 50), and no trace 

 of the culture material must be introduced with the 

 organism. Care must be taken that the culture is 

 young and that only a very small number of organisms 

 are abstracted, as if the preparation is too crowded 

 ifc effectually prevents the flagella from being seen. 

 Great care must also be taken not to overheat the 

 cover-glass with the air-dried specimen in passing it 

 through the flame (see p. 51) ; it is best, in fact, to hold 

 the cover-glass between the finger and thumb instead 

 of using forceps for this operation, as the temperature 

 which is endured by the finger does not injure, but is 

 also quite sufficient for the purpose. The mordant is 

 then run from a pipette on to the cover-glass, and the 

 latter is held over a flame and gently moved up and 

 down the while until the liquid begins slightly to steam. 

 This heating must only last for half to one minute ; the 

 liquid is then poured off, and the cover-glass most 

 thoroughly washed with water ; it is then allowed to 

 dry in the ordinary way, and a few drops of ' aniline- 

 water ' fuchsine solution poured on to it ; it is then gently 

 warmed for about a minute in the flame, after which the 

 stain is washed off very thoroughly with water and the 

 cover-glass is ready for examination. 



The following are the additions of acid and alkali 

 respectively made to the mordant as recommended by 

 Loffler for particular micro-organisms : 



(22 drops = 1 c.c.) 



Spirillum choleras asiaticae . 1 drop of acid to 16 c.c. of mordant 



rubnmi (Esmarch) . 9 drops ,, 



Metchnikomi . 4 ., 



Bacillus pyocyaneus . . 5 .. ,, 



Spirillum concentricum . . .. 



