2-32 TUBERCULOSIS. 



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 agar, 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 ; this mode 

 of growth is specially suitable for the production of tuber- 

 culin (vide infra). 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 

 late years it has been found that growth takes place also on 

 a purely vegetable medium, as was first shown by Pawlowsky 

 in the case of potatoes. Sander has shown that the bacillus 

 grows readily on potato, carrot, macaroni, and on infusion 

 of these substances, especially when glycerine is added. 

 He also found that cultures from tubercular lesions could 

 be more easily made on potato than on glycerine agar. 

 Glycerinated potato can be prepared by covering the slices 



