454 THE TUBERCLE BACILLUS GROUP 



to three hours so as to kill off the contaminating bacteria. Anti- 

 formin does not as a rule kill tubercle bacilli during this time. It 

 is necessary to remove the antiformin by repeated washing and cen- 

 trifugalization of the tubercle bacilli before the latter are inoculated 

 into artificial media, preferably Dorset's egg medium. At best the 

 cultural procedure is an unsatisfactory one. 



(c) Animal Inoculation. Animal inoculation is the most delicate 

 test for demonstrating the presence of tubercle bacilli. Guinea-pigs 

 are the animals selected, and the method of inoculation depends upon 

 the nature of the material. If the material is suspected to contain 

 tubercle bacilli only, it is introduced directly under the skin, or, better, 

 intraperitoneally. If other organisms are associated with the tubercle 

 bacillus, the material mav either be mixed with antiformin and shaken 

 for two hours to kill off or weaken the other organisms, then washed 

 to remove the antiformin and the sediment injected, or the material 

 may be introduced, contaminating organisms and all, subcutaneouslv 

 into a guinea-pig in the following manner. A subcutaneous pocket 

 is made on the flank of the guinea-pig and the suspected material is 

 introduced beneath the skin and pushed forward. The cut is left 

 open and whatever pus-producing organisms are present cause sup- 

 puration; the pus drains away and the initial inflammation is 

 recovered from before the tubercle bacilli kill the animal. Tubercle 

 bacilli then may be recovered from the regional lymph nodes and the 

 internal organs. When the inguinal glands are well enlarged the 

 animal is chloroformed. The skin is sterilized with bichloride of mer- 

 cury and sterile instruments are used in performing the autopsy. 

 Bits of tissue from the lymph glands, spleen, or other organs are 

 removed aseptically and dropped on the surface of specially-prepared 

 media, preferably the Dorset egg medium. A microscopical examina- 

 tion is also made in the usual manner. 



Sputum. It should be remembered that apparently normal indi- 

 viduals may infrequently have acid-fast bacilli in their sputum and, 

 rarely, tubercle bacilli, without producing apparent symptoms. 

 Sputum from suspected tuberculous patients may be examined directly 

 by stained smears, in which case the early morning sputum coming 

 from the depths of the lungs is to be employed. The caseous or puru- 

 lent masses which are characteristic of tubercular sputum are removed, 

 spread upon slides and examined after staining with carbol-fuchsin 

 and decolorizing in the usual manner. If the result is negative, the 

 sputum may be mixed with caustic soda or antiformin, shaken, and 



