1 70 BACTERIOLOG Y. 



cover-slip, which is then to be held over a flame until 

 the solution begins to steam. It should not be boiled. 

 After steaming, the mordant is washed off in water and 

 finally in alcohol. The bacteria are then to be stained 

 in a saturated aniline-water-fuchsin solution. 



There are several points and slight modifications in 

 connection with this method that require to be empha- 

 sized in order to insure success : the culture to be em- 

 ployed should be young, not over 18-20 hours old; it 

 should have developed for this time on fresh agar-agar 

 at 37 to 38 C. ; the mordant should not be perfectly 

 fresh, as the best results are obtained from the use of 

 old solutions that have stood exposed to the air and 

 that have been filtered just before using ; when placed 

 on the cover-slip and held over the flame never heat the 

 mordant to the boiling-point; indeed, the best results are 

 obtained when the preparation is held high above the flame 

 and removed from it at the first evidence of vaporization, 

 or, better still, a little before this point is reached l 



DUCKWAKL'S METHOD 2 is a modification of the Lof- 

 fler method, and the results obtained thereby are very 

 satisfactory. 



Preparation of the Staining Agents. The fixing agent 

 is mordant, and the stain is carbol-gentian-violet or, 

 preferably, carbol-fuchsin. 



The Mordant. 



Desiccated tannic acid 2 grammes. 



Cold saturated solution ferrous sulphate (aqueous) 5 " 



Distilled water 12 c.c. 



Saturated alcoholic solution of fuchsin 1 " 



1 I am indebted to Dr. James Homer Wright, Thomas Scott Fellow 

 in Hygiene, 1892-'93, University of Pennsylvania, for some of the 

 suggestions in connection with the modification of this method. 



2 The Cariner, vol. xx. p. 23. 



