288 MANUAL OF BACTERIOLOGY. 



medium moist. It can be cultivated from tuberculous sputum 

 only with great difficulty. It is best to obtain it from the tis- 

 sues of an animal that has died of tuberculosis, where the 

 tubercle bacilli may be found unmixed with other bacteria. 

 Pieces of tissue should be taken with the precautions necessary 

 to avoid contamination, and should be broken up and rubbed 

 over the surface of the medium. The tubes must be closed 

 with seahng-wax, paraffin or rubber stoppers, or covered with 

 rubber caps, to prevent drying in the incubator. If rubber 



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' A . A 





Fig. 87. — Bacillus Tuberculosis in Sputum, Stained with Fuchsin 



AND MeTHYLENE-BLUE. PHOTOMICROGRAPH IN TwO COLORS. (X lOOO.) 



caps are used, they should first be left in i-iooo bichloride of 

 mercury for an hour, and the cotton plug should be burned 

 before putting on the rubber cap. A number of tubes should 

 be inoculated, using rather large particles of the tuberculous 

 material. Among the tubes inoculated, many will fail to present 

 any growth. After the organism has once been grown upon 

 a culture-medium it may be propagated with less difficulty. 



