APPEARANCES OF CULTURES. 



299 



threads suspended in the liquid. These, on being examined, 

 are seen to be made up of bundles of parallel chains of 

 bacilli. Later, growth is more abundant, and forms a floc- 

 culent mass at the bottom of the fluid. 



In gelatine stab cultures, the charac- 

 teristic appearance can be best observed 

 when a low proportion, say 7^ percent, 

 of gelatine is present, and when the 

 tube is directly inoculated from anthrax 

 blood. In about two days there radiate 

 out into the medium from the needle 

 track numberless very fine spikelets 

 which enable the cultures to be easily 

 recognised. These spikelets are longest 

 at the upper part of the needle track 

 (Fig. 80). Not much spread takes 

 place on the surface of the gelatine, 

 but here liquefaction commences, and 

 gradually spreads down the stab and 

 out into the medium, till the whole of 

 the gelatine may be liquefied. Gelatine 

 slope cultures exhibit a thick felted 

 growth, the edges of which show the 

 wreathed appearance seen in plate cul- 

 tures. Liquefaction here soon ploughs 

 a trough in the surface of the medium. 

 Sometimes " spiking " does not take 



place in gelatine stab cultures, only FIG. 80. Stab 



little round particles of growth occurring culture of the anthrax 



bacillus in peptone- 

 gelatine ; seven days' 

 growth. It shows the 



down the needle track, followed by 

 liquefaction. As has been shown by 

 Richard Muir, this property of spiking "spiking" and also, 



at the surface, com- 

 mencing liquefaction. 

 Natural size. 



can be restored by growing the bacillus 



for twenty-four hours on blood agar at 



37 C. Agar sloped cultures have the 



appearance of similar cultures in gelatine, though, of course, 



no liquefaction takes place. 



Blood serum sloped cultures present the same appear- 



