PATHOGENIC BACTERIA. 277 



tually also mice and guinea-pigs, which are extremely sus- 

 ceptible to anthrax. Small doses of a culture of extremely 

 weak virulence are given to the animals which it is desired 

 to protect, like cattle and sheep (never human beings), and 

 subsequently a somewhat more virulent culture is employed. 1 



FI<;. 75 



Anthrax bacilli in the capillaries of the liver of a mouse, sketched from 

 a section stained with fuchdn. 



Bacillus influenzas. A small bacillus, .2 to .3 j*. by .5 IJL 

 with rounded ends. It does not form spores, is not motile, 

 and is decolorized by Gram's method. It is aerobic, grows 

 only in the incubator, and upon media containing hemo- 

 globin. The medium is prepared by smearing sterile blood 

 over the surface of a tube of agar. Fresh, uncoagulated 

 blood may, with care, be mixed with melted agar sufficiently 

 cooled; the mixture may be poured into tubes and slanted; 



1 For details as to the results of this method, see V. A. Moore, " In- 

 fectious Diseases of Animals," 1902. For other and unique researches on 

 immunity for anthrax see Emmerich, Centralblatt f. Bakteriologie, Orig. 

 Bd. XXXII, p. 821. 



