302 VETERINARY BACTERIOLOGY 



Distribution. The organism is common in garden-soil, par- 

 ticularly that contaminated with excreta. 



Morphology and Staining. B. welchii is a rod, 1 by 3 to 6 /w, 

 with rounded ends when single or truncate when in chains. It 

 frequently occurs in chains, but may be found in pairs and small 

 groups. It is non-motile. In this respect it differs from the other 

 members of this group. Spores are produced only under certain 

 conditions. They are developed best upon the surface of blood- 

 serum in anaerobic cultures. They are central, and the cells 

 develop as clostridia. Capsules may be demonstrated in the body 

 fluids and in some artificial media. The organism stains readily 



with the common anilin dyes 

 and is gram-positive. Involu- 

 tion forms are frequent in arti- 

 ficial media. 



Isolation and Culture. 



^ ; McCampbell has described a 



modification of Welch's method 

 of isolation as follows: " 1 gm. 



| *s ,T- of soil is shaken in sterile NaCl 



solution (0.85 per cent.), and 



% inoculated into sterile neutral 



litmus milk tubes, which are 



Fig. 153. Bacillus welchii (Jordan), covered with 25 mm. of neutral 



paraffin oil, for the purpose of 



securing anaerobiosis, and then incubated for twenty-four hours 

 at 37. At the end of this time the milk in the tubes is coagu- 

 lated and shows acids and gas. A subculture is made in a second 

 litmus milk tube under oil, and incubated for twelve hours in 

 order to prevent the possible overgrowth of other bacteria. At 

 the end of this time the milk usually shows coagulation, acid- and 

 gas-production, as in the first instance ("stormy fermentation"); 

 0.5 c.c. of the whey in the subculture is then injected into the 

 posterior auricular vein of a rabbit. In three or four minutes 

 the animal is killed by a blow on the head, and the body is in- 

 cubated at 37 for eight to ten hours, at the end of which time 

 the abdomen is markedly distended with gas. W r hen ignited, this 

 explodes and burns with a hydrogen flame. The thorax of the 



