CULTIVATION OF TUBERCLE BACILLUS 267 



The growth has practically the same characters as on serum, but 

 is more luxuriant. In glycerin 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 tuberculin (vide infra). The culture has 

 a peculiar fruity and not unpleasant odour. On ordinary agar 

 and on gelatin media no growth takes place. The use of animal 

 tissues in glycerine bouillon as a medium for the growth of the 

 tubercle bacillus has been recently introduced by Frugoni, and 

 is one which gives excellent results. He recommends that small 

 wedges of rabbit's lung should be sterilised in the autoclave, and 

 placed in tubes of glycerine bouillon in such a way that their 

 surface is kept moist by the medium, without the fragments 

 being submerged. The growth is probably more rapid and 

 luxuriant than in any other method. 



Use of Egg Media. Within recent years media containing 

 either the yolk or both the yolk and the white of egg have been 

 used for the culture of the tubercle bacillus by Dorset and others. 

 The following is Dorset's method : The contents of four eggs 

 are well beat, 25 c.c. of water are added and thoroughly mixed, 

 the mixture being passed through muslin to remove air bells. 

 The fluid is then filled into tubes, and these are heated for four 

 hours in the sloped position at 70 C. Before the inoculation of 

 a tube, two drops of sterilised water are placed on the surface. 

 The inoculation material is well rubbed over the surface of the 

 medium, the tubes are sealed with a few drops of paraffin on the 

 top of the plug and are incubated in the sloped position. 

 Vigorous growth takes place on such media, having, generally 

 speaking, the naked eye characters seen in blood serum cultures. 



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 found that the 

 bacillus grew readily on potato, carrot, macaroni, and on infusion of 

 these substances, especially when glycerin was added. He also found 

 that cultures from tubercular lesions could be obtained on glycerin potato 

 (p. 46). 



The optimum tcmi>craturc tor growth is 37 to 38 C. 

 Growth ceases about 42 and usually below 28, but on long- 

 continued cultivation outside the body and in special circum- 

 stances, growth may take place at a lower temperature, e.g. 



