896 SUMMARY OF CURRENT RESEARCHES RELATING TO 



out, and the bacillus is stained so deeply and differentiated so fully 

 from the surrounding substance that it can be seen with the greatest 

 ease with an ordinary |-inch object-glass and daylight, the previous 

 processes having stained it so faintly that high power or artificial 

 illumination were required. The colours used are magenta crystals, 

 which stain the bacillus, and chrysoidin, which stains only the sur- 

 rounding substance. It is a brown which does not stain so intensely 

 as vesuvin. The formulas are : — 



Magenta crystals 2 grammes. 



Pure aniline 3 „ 



Alcohol (sp. gr. • 830) 20 ccm. 



Distilled water 20 ccm. 



Dissolve the aniline in the spirit, rub up the magenta in a glass 

 mortar, adding the spirit gradually until it is all dissolved, then add 

 the water slowly, while stirring, and keep in a stoppered bottle. 



Make a saturated solution of chrysoidin in distilled water and add 

 a crystal of thymol, dissolved in a little absolute alcohol, to make it 

 keep ; a dilute solution of nitric acid (coml.) is also required, one part 

 of acid to two of distilled water. 



The object of the process is to stain the sputum, or section, as the 

 case may be, with a colour which the dilute nitric acid will remove 

 from everything but the tubercle bacillus, and the subsequent staining 

 with chrysoidin is only required to throw up the stained bacillus and 

 make it more prominent. In Dr. Ehrlich's process, the stain for the 

 bacillus is too faint, and the vesuvin, used to stain the ground sub- 

 stance, too opaque; consequently the bacillus appears a faint pink 

 colour on a dense yellowish brown ground, and is not easily made out 

 without high power or special illumination. His method of dissolving 

 aniline in water, in which it is very sparingly soluble, is also open to 

 objection, as it is very apt to vary in the amount taken up by the 

 water. 



For sputum the following process is the most simple. Spread a 

 thin layer on a cover- glass and let it dry ; when quite dry pass it two 

 or three times through the flame of a small Bunsen burner and let it 

 cool. Filter two or three drops of magenta solution in a watch-glass, 

 place the cover-glass with the sputum downwards on the stain, taking 

 care there are no air bubbles under it. Let it remain for fifteen or 

 twenty minutes, then wash in the dilute acid until all colour has dis- 

 appeared, remove the acid with distilled water, when a faint colour 

 will return ; then place the cover-glass in the same manner as before 

 on a few drops of chrysoidin filtered into the bottom of a watch-glass, 

 and let it remain a few minutes until it has taken on the brown stain ; 

 wash off the superfluous colour in distilled water and place the cover- 

 glass in absolute alcohol for a few minutes, remove and dry perfectly 

 in the air, place a drop of Canada balsam solution on the cover-glass 

 and mount. It is better to use small glass funnels for filtering the 

 stains, as they protect the fingers. Sections of hardened tissue are 

 treated in the same manner with the necessary modifications. 



With regard to the powers required to examine the bacilli after 



