334 Gaseous Edema 



resist desiccation and exposure to the air for ten months. They 

 stain readily in hot solutions of fuchsin in anilin water, and are not 

 decolorized by a moderate exposure to the action of 3 per cent, solu- 

 tion of hydrochloric acid in absolute alcohol. They are oval, and 

 are usually situated near the ijaiddle of the bacillus, which is distended 

 because of the large size of the spore and bulges at the sides. 



Staining. — The organism stains well with the ordinary stains, 

 and retains the color well in Gram's method. When stained with 

 methylene-blue a granular or vacuolated appearance, is sometimes 

 observed, due to the presence of unstained dots in the cytoplasm. 



Usually in the body-fluids and often in cultures the bacilli are 

 surrounded by distinct capsules — clear, unstained zones. To dem- 

 onstrate this capsule to the best advantage, Welch and Nuttall de- 

 vised -the following special stain : 



A cover is thinly spread with the bacilli, dried, and fixed without 

 overheating. Upon the surface prepared, glacial acetic acid is 

 dropped for a few moments, then allowed to drain off, and at once 

 replaced by a strong aqueous solution 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 solu- 

 tion, 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 capsules. After mounting in Canada balsam the capsules 

 are not nearly so distinct. 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 immediately about the bacillus. 



Cultivation. — The bacillus is anaerobic and aerogenic. It grows 

 upon all culture media at the room temperature, though better at 

 the temperature of incubation. 



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 demonstrated by tilting the tube 

 and observing 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 pre- 

 cautions 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 un- 

 less such tubes are placed in a Buchner's jar or other anaerobic 

 device. The deeper colonies are the largest. Sometimes the growth 

 takes place within 10-12 mm. of the surface; at others, within 3-4 

 cm. of it. After repeated cultivation the organisms seem to become 



