THE METHOD OF VAN ERMENGEM. 151 



37 to 38 C. ; the solutions should not be perfectly fresh, 

 as the best results are obtained from the use of old solu- 

 tions 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. We have derived no 

 advantage from the addition of acids or alkalies to the 

 mordant as recommended by Loeffler, but obtain, with a 

 fair degree of regularity, satisfactory results through the 

 use of the neutral mordant alone. 1 



BUNGE'S METHOD. A useful modification of Loeffler's 

 method is that recommenced by Bunge : prepare a satu- 

 rated solution of tannin, and a solution of liquor ferri 

 sesquichlor. of the strength of 1 : 20 of distilled water. 

 To 3 parts of the tannin solution add 1 part of the dilute 

 iron solution. To 10 c.c. of such a mixture add 1 c.c. 

 of concentrated watery solution of fuchsin. This mor- 

 dant is not to be used fresh, but only after standing ex- 

 posed to the air for several days (better for several 

 weeks). After preparing the cover-slip with all pre- 

 cautions necessary to cleanliness the filtered mordant is 

 allowed to act cold for about five minutes, after which 

 it is slightly warmed ; the slip is then washed off in 

 water, dried, and faintly stained with carbol fuchsin. No 

 addition of acid or alkali to the mordant is necessary. 



THE METHOD OF VAN ERMENGEM. Another 

 method of demonstrating the presence of flagella is 



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

 giene, 1892-93, University of Pennsylvania, for some of the suggestions in 

 connection with the modification of this method. 



