170 TETANUS, MALIGNANT (EDEMA, ETC. 



in addition to other points, between it and the Bacillus 

 anthracis. 



Immunity. One attack of the disease, if not fatal, affords 

 protection against future attacks. 



Active immunization has been practised on animals with 

 extracts of infected meats. The first vaccine used consists of 

 about 0.01 gm. of dried extract previously heated to 100 C. 

 for five or six hours. This is emulsified with 0.85 per cent, 

 saline solution. In about ten days a similar amount of the 

 second vaccine is given. In this instance the extract has 

 been heated to 90 C. only. These vaccines should be in- 

 jected under strict aseptic precautions near the end of the 

 tail of the animal. 



Bacillus Aerogenes Capsulatus. 



History. This bacillus was discovered by Welch and de- 

 scribed by Welch and Nuttall in 1892. 



Morphology and Staining. It resembles slightly the anthrax 

 bacillus. It is very variable in size, however, varying in length 

 from 36 //., sometimes being nearly as broad as long, especially 

 in artificial cultures. Generally they occur singly, but occasion- 

 ally in chains. Long chains are found in the blood, but never, 

 in artificial media. This is considered by Welch a great point 

 of differentiation from the Bacillus anthracis. 



The bacillus of Welch is non-flag 'ellated, non-motile, and 

 constantly capsulated. It stains by all the ordinary anilin 

 stains and by Gram's stain. Sometimes involution forms on 

 artificial media give up the stain. 



Biology. It is an obligatory anaerobe, growing well on all 

 media, producing in deep stab culture characteristic gas-bub- 

 bles. 



Pathogenesis. It is slightly pathogenic for rabbits, highly 

 so for guinea-pigs. In man, in infected compound fractures 

 and in puerperal infections, it has been found. Gangrene 

 foudroyante (emphysematotis gangrene) seems to be due to 

 infection by Welch's bacillus. It has been found in some 

 instances in the apparently normal intestine. 



