STAINING TUBERCLE BACTERIA 55 



EXERCISE XXI 



STAINING TUBERCLE BACTERIA (BACILLI) 



84. The stained tubercle bacterium possesses the power of 

 retaining the coloring matter even when treated with a strong 

 decolorizer, such as a solution of sulphuric or nitric acid. On 

 this account staining has a high differential value which is made 

 use of in identifying this organism. Thus, in the examination 

 of sputum in cases of suspected tuberculosis, the object is to 

 determine the presence of tubercle bacteria. As this organism 

 is not easily cultivated, the staining process is very largely de- 

 pended upon in making a differential diagnosis. 



85. Work for this Exercise. — Make 4 cover-glass prepa- 

 rations from a culture of tubercle (furnished). Stain two of 

 them with tubercle stain and carefully describe the appearance 

 of the bacteria and illustrate them with a few drawings. 



Stain two of the preparations after Gram's method. 



Stain a cover-glass preparation of tubercular sputum (fur- 

 nished). 



Read the directions in the text-books for staining tubercle 

 bacteria (bacilli). 



86. Staining Tubercle Bacteria. — Prepare the cover-glass 

 preparations from the culture of tubercle bacteria and flame 

 them as already described. Stain in fresh carbOl fuchsin. 

 Place a few drops of the stain on the film side of the cover- 

 glass and hold it over a flame with forceps until steam is given 

 off. Allow the hot stain to act for from 3 to 5 minutes. Or 

 the preparation may be floated on the carbol fuchsin in a watch- 

 glass without heat. In this case it is allowed to act for from 10 

 to 15 minutes. The preparation is then rinsed in water and 

 decolorized by treating it with a 10% solution of nitric or sul- 

 phuric acid for ^ to i minute. It is again rinsed in water 

 when it is ready for examination. It can be dried and mounted 



