BACILLUS ANTHRACIS 29 



The intimate structure of the colony, and espe- 

 cially of the free margin, is shown in Fig. 8, which 

 represents a highly magnified view of the edge of 

 such an impression preparation. 



In the colony represented the border is quite 

 unbroken, but not rarely individual lines of bacilli 

 break from the edge and pass over the surface of 

 the medium, and occasionally the colony is sur- 

 rounded by shaggy-hair-like processes (Medusa- 

 head colonies). In the depths of the medium the 

 colonies are more spherical, granular, and brown. 

 Slow liquefaction takes place. 



Animals can be infected with anthrax either by 

 inoculation or by the inhalation or ingestion of the 

 bacilli. Though there are certain local differences 

 due to the point of entrance of the bacillus, and 

 though the symptomatology may differ, yet the 

 microscopic appearances presented by the blood 

 and by sections of the internal organs are in all 

 cases those characteristic of an acute septicaemia. 

 Beyond a general congestion there is very little 

 structural change in the tissues, and the microscopic 

 appearance presented is that of a general injection 

 of the blood-vessels, especially of the smaller arteries 

 and capillaries, with bacilli. Anthrax bacilli in- 

 crease with enormous rapidity in the body of a 



