CULTURING THE TUBERCLE BACILLI OF MILK 135 



of the special medium in Petri dishes. The medium used (Hesse's 

 agar) is made as follows: 



Nutrose (sodium caseinate) 5 grams. 



Sodium chloride 30 grams. 



Glycerin 30 grams. 



Agar 10 grams. 



Na 2 CO 2 (crystalline) solution (28.6 per cent.) 5 cc. 



Distilled water 1000 cc. 



Mix ingredients. Heat until agar is dissolved. Filter through 

 cotton. Pour into Petri dishes. Sterilize fractionally. 



After inoculating two or three Petri dishes in the manner 

 indicated, incubate at 37.5 C. in a moisture-saturated atmosphere 

 for several days. If tubercle bacilli are present young colonies 

 will appear which may be identified with a low power by the resem- 

 blance to broken wavy lines. 



Instead of making the glass-slip smears as above suggested, 

 good results may be obtained through the use of the cotton throat 

 swabs such as are used by physicians for taking throat cultures in 

 diphtheria cases. Dip or roll the cotton ends of three swabs in 

 the suspected tuberculous material, suspend in air until perfectly 

 dry and then place in drying over (100 C.) for 15 min., then rub 

 the cotton over the surface of the special culture medium in Petri 

 dishes. Make some six or seven parallel streaks over the surface of 

 the medium. Incubate and examine as before. Should the glass- 

 slip or cotton-swab preparations be placed in the drying oven 

 before air drying them, all or nearly all of the tubercle bacilli would 

 be killed in the drying oven. 



Several investigators have recommended a direct method of 

 examination for ascertaining the presence of tubercle bacilli in 

 milk, and in other materials, through the use of agents which will 

 completely dissolve all bacterial bodies excepting the acid-fast 

 group of organisms to which the tubercle bacillus belongs. For 

 this purpose antiformin (really a mixture of chlorinated sodium 

 hypochlorite and Labarraque's solution) has been highly recom- 



