THE USE OF STRONGER STAINING SOLUTIONS. 115 



and blue bacilli are to be seen, and as the species also 

 differ morphologically, it can be immediately recog- 

 nised that the difference of colour tallies with the 

 difference of form. 



Sputum, containing tubercle bacilli, affords excellent 

 material for this ■ contrast-staining ; it is, moreover, 

 very easily obtained. The small yellowish cheesy 

 nodules, which are distributed about in the thin 

 viscous fluid of the sputum are generally exceedingly 

 rich in tubercle bacilli. We take such a nodule, and 

 place it upon one end of a slide ; then we place 

 another slide over the first, and rub it with a some- 

 what lingering pressure over the under one until the 

 nodule is pressed out into an evenly-distributed layer. 

 A minute quantity of this is then taken up with a 

 platinum wire, and is spread out as evenly and thinly 

 as possible upon a cover-glass, which is completely 

 dried in the air, and is then fixed in the usual manner. 

 It may be passed more frequently through the flame 

 than most cover-glass preparations, as the tubercle 

 bacilli are very resistant ; but it is not necessary to 

 do so. A little aniline water solution of fuchsine, or 

 Ziehl's carbolic fuchsine is then placed on the cover- 

 glass. If no heat is applied, the staining solution 

 must be left in contact with the sputum for from five 

 to ten minutes. If the liquid is warmed until steam 

 begins to be formed, and is then kept at this tempera- 

 ture, only about two minutes are required. 



