534 BACTERIOLOGY. 



smaller ; it does not develop into long threads in the 

 tissues ; it is more actively motile, and forms spores 

 more readily in the tissues of the animal than does the 

 bacillus of malignant oedema. In their relation to ani- 

 mals they also differ ; for instance, cattle, while con- 

 spicuously susceptible to symptomatic anthrax, are prac- 

 tically immune from malignant oedema ; and while swine, 

 dogs, rabbits, chickens, and pigeons are readily infected 

 with malignant oedema, they are not, as a rule, suscepti- 

 ble to symptomatic anthrax Horses are affected only 

 locally, and not seriously, by the bacillus of symptomatic 

 anthrax ; but they are conspicuously susceptible to both 

 artificial inoculation and natural infection by the bacil- 

 lus of malignant oedema. 



The distribution of the two organisms over the earth's 

 surface is also quite different. The oedema bacillus is 

 present in almost all soils, while the bacillus of symp- 

 tomatic anthrax appears to be confined to certain locali- 

 ties, especially places over which infected herds have 

 been pastured. 



A single attack of symptomatic anthrax, if not fatal, 

 affords subsequent protection ; while infection with the 

 malignant oedema bacillus appears to predispose to re- 

 currence of the disease. (Baumgarten.) 



BACTERIUM WELCHII, MIGULA, 1900. 

 Synonym : Bacillus aerogenes capsulatus, Welch and Nuttall, 1892. 



This organism consists of straight or slightly curved 

 rods with rounded ends, somewhat thicker than bacte- 

 rium anthracis, varying in length ranging from 3 to 6 

 microns ; sometimes longer chains or threads are seen. 

 The rods are surrounded by a transparent capsule, 

 whether grown in artificial media or obtained from 



