THE BACILLUS OF ANTHRAX. 



329 



varies considerably in different culture media ; and in old cultures 

 irregular forms are frequently seen " involution forms." 



Under favorable conditions endogenous spores are developed in 

 the long filaments which grow out in artificial culture media. 

 These first appear as refractive granules distributed at regular inter- 

 vals in the segments of the protoplasm, which gradually disappear 

 as the spores are developed ; and these are left as oval, highly re- 

 fractive bodies, held together in a linear series by the cellular enve- 

 lope, and subsequently set free by its dissolution. The germination 

 of these reproductive bodies results in the formation of rods and 

 spore-bearing filaments like those heretofore described. In this pro- 

 cess the spore is first observed to 

 lose its brilliancy, from the ab- 

 sorption of moisture, a promi- 

 nence occurs at one end of the 

 oval body, and soon the external 

 envelope exosporium is rup- 

 tured, permitting the softened 

 protoplasmic contents enclosed 

 in the internal spore membrane 

 endosporium to escape as a 

 short rod, to which the empty 

 exosporium sometimes remains 

 attached. 



The anthrax bacillus stains 

 readily with the aniline colors 

 and also by Gram's method, 

 when not left too long in the 

 decolorizing iodine solution. 

 Loffler's solution of methylene 

 blue is an especially good stain- 

 ing fluid for this as well as for many other bacilli. Bismarck brown 

 is well adapted for specimens which are to be photographed, and also 

 for permanent preparations, as it is less liable to fade than the blue 

 and some other aniline colors. 



Biological Characters. The anthrax bacillus is aerobic, but 

 not strictly so, as is shown by the fact that it grows to the bottom of 

 the line of puncture in stick cultures in solid media. It is non-mo- 

 tile, and is distinguished by this character from certain common 

 bacilli resembling it in morphology Bacillus subtilis which were 

 frequently confounded with it in the earlier days of bacteriological 

 investigation. 



The anthrax bacillus grows in a variety of nutrient media at a 

 25 



FIG. 101. Bacillus anthracis, from a culture, 

 showing formation of spores. X 1,000. (Klein.) 



