BA GILL US ANTHRA CIS. 553 



upon the surface of which it floats as an irregular, white 

 pellicle. In gelatin stick cultures at first development 

 occurs along the line of puncture as a delicate white 

 thread, from which irregular, hair-like projections soon 

 extend perpendicularly into the culture medium, the 

 growth being most luxuriant near the surface, but con- 

 tinuing also below. At the end of two or three days 

 liquefaction of the medium commences at the surface 

 and gradually progresses downward. 



Growth on Agar. The growth on agar plate cul- 

 tures in the incubator at 37 C. is similar to that on 

 gelatin, and is still more characteristic and beautiful in 

 appearance. A grayish-white layer is formed on the 

 surface within twenty-four hours, which spreads rapidly 

 and is seen to be made up of interlaced threads. 



In bouillon the growth is characterized by the forma- 

 tion of flaky masses, which sink as a sediment to the 

 bottom of the tube, leaving the supernatant liquid clear. 



Spore formation, as already noted, only takes place 

 in the free presence of oxygen, and at a temperature of 

 15 to 43 C. There is no development of spores at a 

 greater depth than 1.5 metres in the earth, or in the 

 bodies of living or dead animals; but spores may be 

 found in the fluids containing the bacilli when these 

 come in contact with the air, as in bloody discharges 

 from the nostrils or from the bowels of the dead animal. 



There are certain non- spore bearing species of an- 

 thrax. Sporeless varieties have also been produced 

 artificially by cultivating the typical anthrax bacillus 

 under unfavorable conditions. The addition of anti- 

 septics, as carbolic acid, favors these conditions. Vari- 

 eties differing in their pathogenic power may also be 

 produced artificially. Pasteur produced an " attenu- 



