and 



CULTURAL CHARACTERISTICS 



319 



and sow the medium from an agar culture or with pieces of tuberculous tissue which 

 have been carefully crushed. The material used for sowing should float on the sur- 

 face of the vaseline or between the vaseline and the broth. Should it fall to the 

 bottom it is only necessary to shake the flask carefully and the drops of oil will 

 float the material to the surface again. To make microscopical preparations blot 

 up the oil from the slide with blotting paper. 



7th Generation 



5 weeks old. 



FIG. 209. A culture of the human tubercle bacillus on glycerin broth. The 

 culture was isolated from the lung of a man aged 33, who died of phthisis ; it 

 grew luxuriantly on all media containing glycerin, was virulent for chimpanzees, 

 monkeys and guinea-pigs but had only slight virulence for calves, rabbits and 

 horses (A. S. Griffith). (See footnote p. 316.) 



10. Glycerin-fish-broth. This medium has been recommended by Martin. 

 The cultural characteristics are the same as on ordinary glycerin-broth. 



Mince the flesh of an herring and add to it one and half times its weight 

 of water. Heat slowly and keep it boiling for three-quarters of an hour. 

 Filter through Chardin paper several times while warm and when clear add 

 6 per cent, of glycerin. Neutralize if necessary. Distribute in tubes and 

 sterilize in the autoclave. 



