6 9 

 EXERCISE XXXVIII. 



BACTERIUM (BACILLUS) OF TUBERCULOSIS. 



1 13. Explanatory note. The tubercle bacterium does 

 not grow readily on the ordinary media. For its cultivation 

 blood serum, glycerine agar, or bouillon containing 5 to 7% 

 glycerine are ordinarily used. It is with much difficulty 

 that it is made to grow from lesions in tuberculous animals, 

 but when a culture is once started it can, on the media men- 

 tioned above, and sometimes on agar, be cultivated in sub- 

 cultures with comparative ease. It grows very slowly and 

 it is necessary that the temperature should be kept, without 

 variation, at about 37 C. On account of these difficulties 

 it is not practicable in a general course to cultivate this or- 

 ganism, but cultures on solid and liquid media will be fur- 

 nished by the instructor for examination. It is important, 

 however, to be able to recognize this organism in tissues and 

 sputum and consequently the following additional exercise 

 in staining and study ing it is given. 



114. General directions. Examine and carefully de- 

 scribe the appearance of the cultures of the tubercle bacterium 

 on glycerine agar, and in glycerine bouillon, furnished. 



Make cover-glass preparations from the culture furnished 

 for that purpose, and stain. 



Make 4 cover-glass preparations from tuberculous sputum 

 and .stain for tubercle bacteria. It is often desirable to coun- 

 ter stain the specimens from sputa. Stain 2 of them by 

 Gabbett's method, and 2 with carbol fuchsin and decolorize 

 without counter staining. Make a few (2 or 3) cover-glass 

 preparations from the liver or spleen of a guinea pig, which 

 has died from tuberculosis and stain them for tubercle bac- 

 teria. Stain one with carbol fuchsin and decolorize with 

 sulphuric acid, and stain one by Gabbett's method, and 

 counter-stain. 



