600 APPLICATION OF METHODS OF BACTERIOLOGY 



are affected only locally, and not seriously, by the bacillus 

 of symptomatic anthrax; but they are conspicuously sus- 

 ceptible to both artificial inoculation and natural infection 

 by the bacillus of malignant edema. 



The distribution of the two organisms over the earth's 

 surface is also quite different. The edema bacillus is present 

 in almost all soils, while the bacillus of symptomatic anthrax 

 appears to be confined to certain localities, 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 edema bacillus appears to predispose to recurrence 

 of the disease. (Baumgarten.) 



BACTERIUM WELCHn, MIGULA, 1900. 



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



This organism consists of straight or slightly curved rods 

 with rounded ends, somewhat thicker than bacterium an- 

 thracis, varying in length from 3 to 6/^; sometimes longer 

 chains or threads are seen. The rods are surrounded by a 

 transparent capsule, whether grown in artificial media or 

 obtained from animal bodies. It is a non-motile, spore- 

 forming organism, and is strictly anaerobic in character. 

 It stains with the ordinary aniline dyes and by the Gram 

 method. 



Under anaerobic conditions the organism grows on the 

 usual culture media at room temperature, and forms large 

 quantities of gas in media containing carbohydrates. Gela- 

 tin is not liquefied. In agar-agar the colonies are usually 

 from 1 to 2 millimeters in diameter, but may be as large as 

 1 centimeter in diameter. They have a grayish-white color, 



