BACILLUS (EDEMATI6 MALIGNI. 243 



long threads of the oedema bacilli, and the oedema bacilli 

 are sometimes, though not always, motile, while the 

 anthrax bacilli are always motionless. The most marked 

 morphological difference between the two is, however, the 

 mode of spore formation. In the oedema bacilli this does not 

 occur in the threads in the same way as in 

 the anthrax bacilli, but the individual bacilli $ $ ff ^ 

 show before the spore formation a slight j /> ^j / 

 swelling in the middle or at one end, so f g 



that a spindle or tadpok form results, 



, . , . , , , Fig. 67. Spore 



and in this swollen part the large oval formation in the 

 spore, at first dull, but later highly re- ^f^eSfx 

 fracting, is formed, and when its forma- 700. 

 lion is complete the colourable remains of the bacilli 

 gradually disappear. 



There is considerable difficulty in cultivating the Cultivation of 

 oedema bacilli, because they are marked anaerobes, so bacilli. 61 

 much so that they only form visible colonies when 

 oxygen is pretty completely excluded. They do not 

 grow at all on gelatine plates, even in the deeper layers ; 

 nor do they grow along the inoculation track on gelatine, 

 agar, or blood serum. On the other hand they can 

 grow when they are inoculated at a certain depth in 

 tubes containing nutrient agar or blood serum, in such 

 a manner that the canal of inoculation becomes tightly 

 closed over the material introduced. As Hesse first 

 observed, a diffuse muddiness of the nutritive material 

 consisting of bacilli appears in the nutrient agar, with 

 here and there more markedly muddy lines or clouds. At 

 the, same time gas bubbles are formed within the inocu- 

 lation canal, which penetrate into the agar in various 

 directions, often divide it transversely, and drive up the 

 separated portion as high as the cotton wool plug, and 

 at the same time so compress the agar that a muddy 

 fluid is separated which collects at the bottom of the 

 glass, and contains numerous bacilli. The escaping gas 

 has a slight, somewhat heavy smell. Blood serum is 

 quickly liquefied by the bacilli, and there is at the 

 same time marked development of gas ; in a few days, 

 when kept in an incubator at 37 C., the whole mass 



