BACILLUS ANTHRACIS 



303 



to be made up of bundles of parallel chains of bacilli. Later, 

 growth is more abundant, and forms a flocculent mass at the 

 bottom of the fluid. 



In gelatin stab cultures, the characteristic appearance can be 

 best observed when a low proportion, say 7J per cent, of gelatin 



FIG. 105. Anthrax bacilli, arranged in chains, 

 from a twenty-four hours' culture on agar 

 at 37 C. 



Stained with fuchsin. x 1000. 



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 recog- FlG .i 06 .-Stab culture of 



nised. These spikelets are longest at 



the upper part of the needle track 



(Fig. 106). Not much spread takes 



place on the surface of the gelatin, 



but here liquefaction commences, and 



gradually spreads down the stab and 



out into the medium, till the whole 



of the gelatin may be liquefied. Gelatin slope cultures exhibit 



a thick felted growth, the edges of which show the wreathed 



appearance seen in plate cultures. Liquefaction here soon 



ploughs a trough in the surface of the medium. Sometimes 



"spiking" does not take place in gelatin stab cultures, only 



the anthrax bacillus in 

 peptone-gelatin ; seven 

 days' growth. It shows 

 the "spiking" and also, 

 at the surface, com- 

 mencing liquefaction. 

 Natural size. 



