Cultivation 



663 



.Ou 



of gentian violet, which is poured off 

 and renewed several times until the 

 acid has been replaced by the stain. 

 The specimen is then examined in the 

 coloring solution, after soaking up the 

 excess with filter paper, the thin layer 

 of coloring fluid not interfering with a 

 clear view of the bacteria and their cap- 

 sules. After mounting in Canada bal- 

 sam the capsules are not nearly so dis- 

 tinct. The width of the capsule varies 

 from one-half to twice the thickness of 

 the bacillus. Its outer margin is 

 stained, leaving a clear zone immedi- 

 ately about the bacillus. 



The bacillus is anaerobic and aero- 

 genie. It grows upon all culture media 

 at the room temperature, though bet- 

 ter at the temperature of incubation. 



Cultivation. Gelatin. It grows in 

 ordinary neutral or alkaline gelatin, 

 but better in gelatin containing 

 glucose, in which the characteristic 

 gas-production is marked. Soft media, 

 made with 5 instead of 10 per cent, of 

 the crude gelatin, is said to be better 

 than the standard preparation. 



There is no distinct liquefaction of 

 the medium, but in 5 per cent, gelatin 

 softening can sometimes be demon- 

 strated by tilting the tube and observ- 

 ing that the gas bubbles change their 

 position, as well as by noticing that 

 the growth tends to sediment. 



Agar-agar. In making agar-agar 

 cultures careful anaerobic precautions 

 must be observed. The tubes should 

 contain considerably more than the 

 usual quantity of the medium, which 

 should be boiled and freshly solidified 

 before using. The implantation should 



be deeply made with a long wire. The growth takes place 

 slowly unless such tubes are placed in a Buchner's jar or 



Fig. 200. Bacillus 

 aerogenes capsulatus, 

 with gas-production 

 (from photograph by 

 Prof. Simon Flexner). 



