NON-SPORING BACILLI 275 



growth direct from the tissues, blood serum and Dorset's 

 egg media are commonly used. 



On blood serum, at 37-5 C, growth appears in ten to 

 fourteen days as minute spots, rather irregular, raised 

 above the surface, and comparable to small dry scales. 

 The culture is got by inoculating with a sterile platinum 

 loop from foci in a tuberculous gland ; or by planting an 

 actual piece of tissue on to the surface of the serum ; or 

 by inoculating with tubercle bacilli, derived by the 

 anti-formin method (see later) from sputum or digested 

 tissue. 



On Dorset's egg media, vigorous growth takes place 

 resembling that on blood serum. To make the medium : 

 take the whole contents of four eggs, beat well, add 25 c.c. 

 of water, and mix thoroughly ; filter through muslin to 

 remove air bells ; fill into tubes, and heat these in 

 sloped position for four hours at 70 C. They are 

 now ready ; but before inoculation, two drops of steri- 

 lized water are placed on the surface of the medium. 

 When inoculating, the material is well rubbed over the 

 surface, the plug is replaced, and is sealed over with a 

 few drops of paraffin, and the tube incubated in the 

 sloped position. 



On glycerin potato, growth takes place, and on other 

 purely vegetable media. 



Optimum Conditions. B. tuberculosis is markedly aerobic. 

 It grows at human blood-heat, 37 to 38 C. The usual 

 range is 28 to 42 C. but it can be acclimatized to grow 

 at 22 to 23 C. In fluid media it is killed in fifteen to twenty 

 minutes at 6o C, in five minutes at 8o C, and in one to 

 two minutes at 90 C. It can resist dry heat at ioo C. for 

 one hour. Simple drying is not efficient, as still virulent 

 forms have been found in dried tuberculous sputum after 

 two months. Similarly, putrefaction of sputa or tissue does 

 not destroy the bacilli readily, for they have been found 

 aliyo under such conditions after three weeks. Gastric 

 juice failed to kill them in six hours, and several three- 

 hour spells of freezing at 3 C. had little effect. Direct 

 sunlight rapidly kills them ; 5 per cent carbolic kills them 

 in a few minutes, but if, as in sputum, they are protected 

 by mucus, complete disinfection takes five to six hours. 



