BACTERIOLOGICAL EXAMINATION 295 



The thin copper lid of the kettle will, a few minutes after the toluol has begun 

 to boil, reach the temperature of the boiling point of toluol (111° C). Upon 

 the plate heated in this manner the cover-glasses with the dried blood are 

 placed for thirty to sixty seconds, and this fixation is quite sufficient for most 

 of the staining methods. 



Among the methods of staining the blood those of Ehrlich have shown 

 themselves to be the most successful. In particular his triacid solution, which 

 in its application is quite simple, brings out a great many points, and fur- 

 nishes reliable conclusions. The formula for its preparation is the following : 



The three stains, orange G-, acid fuchsin and methylene green, are prepared 

 in saturated aqueous solutions, and are mixed in the following amounts and 

 order (with thorough shaking during the process) : 



Orange G 13-14 c.c. 



Acid fuchsin 6-7 " 



Aq. dest 15 " 



Alcohol 15 " 



Methyl green 25.5 " 



Alcohol 10 " 



Glycerin 10 " 



If the fixed blood preparation is allowed to float for about five minutes 

 upon a few drops of this staining solution, the staining is finished. There 

 is no danger of over-staining, even in a decidedly longer duration of staining. 

 The cover-glass is then thoroughly rinsed in water, carefully dried between 

 blotting papers and mounted in Canada balsam. 



For certain purposes, as we shall see later on, this triacid solution is not 

 suitable, and we are compelled occasionally to use complementary stainings 

 with methylene-blue, or with methylene-blue eosin mixtures. Formulae for 

 such stains are the following: 



Very instructive pictures are obtained if we stain for half a minute with 

 a solution of 0.5 eosin to 100 c.c. of a 60 per cent, alcohol, rinse in water, 

 and subsequently stain for two minutes with a watery methylene-blue solution 

 of 1-250. 



Specimens of great clearness and elegance are obtained by a careful appli- 

 cation of the Chenzinsky's methylene-blue eosin mixture : 



Concentrated watery methylene-blue solution 40 c.c. 



0.5 per cent, eosin solution in 70 per cent, of alcohol. . . 20 " 

 Distilled water 40 " 



This solution must be filtered each time prior to use ; the staining requires 

 from six to twenty-four hours and, to prevent evaporation and the precipita- 

 tion of the staining material, must be carried out in air-tight closed cups. 



By the aid of these staining methods we are enabled to recognize a number 

 of the peculiarities of the blood cells, which are indistinct or entirely unrecog- 

 nizable in fresh blood. Some of the newer, particularly the so-called " uni- 

 versal," stains have such glaring faults that,' at least for the present, they 



