STEEPTOOOCOUS SEPTIOUS 165 



the bacilli, after which the process of cultivation on plates 

 is proceeded with, by preference in an atmosphere of hydro- 

 gen. One or two per cent, of grape-sngar maj' be added to 

 the gelatine with advantage. ' The plates show colonies which 

 have a halo radiating in all directions, and liquefaction sets 

 in slowly, being combined with the formation of gas (fig. 

 62). In high cultures a cloud radiating in all directions 

 develops, which liquefies later on. 



If an infection is made with a pure culture, the rods are 

 found only on the site of inoculation and in its immediate 

 neighbourhood. 



To destroy the spores, they must be exposed for five 

 minutes to the action of steam at 100° C. 



Streptococcus septicns. — Nicolaier and Guarneri found 

 the Streptococcus septicus in impure earth. It does not ex- 

 hibit a chain form in aU cases, and occurs in the organs 

 of infected animals in the shape of diplococci. Gelatine is 

 not liquefied, and little dots develop on the plate at room 

 temperature. If mice are inoculated with irnpure earth 

 they invariably die within three days ; paralytic symptoms 

 occur in the posterior extremities before death, and diplo- 

 cocci are found everywhere in the organs and the blood, 

 and may block the vessels. 



Bacillus anthracis, — This bacillus is also found on the 

 surface of the ground, and its rods were seen by Pollender 

 as long ago as 1849 in the blood of animals suffering from 

 anthrax, although they were first thoroughly investigated 

 by Koch. According to Pasteur, they are spread by earth- 

 worms. 



They are large even rods with abruptly cut ends, 

 arranged in chains which consist of segments of varying 

 length (fig. 63), and are immotile, such movements of 

 single bacteria as are now and then seen being apparently 

 only caused by currents in the fluid. They grow at room 



