CULTIVATION OF TUBERCLE BACILLUS. 213 



occur close together. Koch compared the appearance of 

 these to that of small dry scales. In sub-cultures, however, 

 growth is more luxuriant and may come to form a dull wrinkled 

 film of whitish colour, which may cover the greater part of 

 the surface of the serum and at the bottom of the tube may 

 grow over the surface of the condensation water on to the 

 glass (Fig. 58, A). The growth is always of a dull appearance 

 and has a considerable degree of consistence, it being difficult 

 to dissociate a portion thoroughly in a drop of water. In 

 older cultures the growth may acquire a slightly brownish 

 or buff colour. When the small colonies are examined under 

 a low power of the microscope they are seen to be extending 

 at the periphery in the form of wavy or sinuous streaks 

 which radiate outward and which have been compared to 

 the flourishes of a pen. The central part shows similar 

 markings closely interwoven. These streaks are composed 

 of masses of the bacilli arranged in a more or less parallel 

 manner. 



On glycerine cigar, which was first introduced by Nocard 

 and Roux as a medium for the culture of the tubercle 

 bacillus, growth takes place in sub-cultures at an earlier date 

 and progresses more rapidly than on serum, but, strangely 

 enough, this medium is not suitable for obtaining cultures 

 from the tissues, inoculations with tubercular material usually 

 yielding a negative result. The growth has practically the 

 same characters as on serum, but is more luxuriant. It, 

 however, tends to lose its virulence more rapidly than when 

 grown on serum. In glycerine broth, especially when the 

 layer is not deep, tubercle bacilli grow readily in the 

 form of little white masses which fall to the bottom and 

 form a powdery layer. If, however, the growth be started 

 on the surface it spreads superficially as a dull whitish, 

 wrinkled pellicle which may reach the walls of the flask. 

 The culture has a peculiar fruity and not unpleasant odour. 

 On ordinary agar and on gelatine media no growth takes 

 place. 



It was at one time believed that the tubercle bacillus 

 would only grow on media containing animal fluids, but of 



