FERMENTATION 299 



activity of the contagium, and that was the inoculation 

 with it of living animals. He operated upon guinea-pigs 

 and rabbits, but the vast majority of his experiments were 

 made upon mice. Inoculating them with the fresh blood 

 of an animal suffering from splenic fever, they invariably 

 died of the same disease within twenty or thirty hours 

 after inoculation. He then sought to determine how the 

 contagium maintained its vitality. Drying the infectious 

 blood containing the rod-like organisms, in which, how- 

 ever, the spores were not developed, he found the con- 

 tagium to be that which Dr. Sanderson calls "fugitive." 

 It maintained its power of infection for five weeks at the 

 furthest. He then dried blood containing the fully-devel- 

 oped spores, and exposed the substance to a variety of 

 conditions. He permitted the dried blood to assume the 

 form of dust; wetted this dust, allowed it to dry again, 

 permitted it to remain for an indefinite time in the midst 

 of putrefying matter, and subjected \t to various other 

 tests. After keeping the spore-charged blood which had 

 been treated in this fashion for four years, he inoculated a 

 number of mice with it, and found its action as fatal as that 

 of blood fresh from the veins of an animal suffering from 

 splenic fever. There was no single escape from death after 

 inoculation by this deadly contagium. Uncounted millions 

 of these spores are developed in the body of every animal 

 which has died of splenic fever, and every spore of these 

 millions is competent to produce the disease. The name 

 of this formidable parasite is Bacillus anihracis.^ 



^ Koch found that to produce its characteristic ejffects the contagium of 

 splenic fever must enter the blood ; the virulently infective spleen of a diseased 

 animal may be eaten with impunity by mice. On the other hand, the disease 

 refuses to be communicated by inoculation to dogs, partridges, or sparrows. In 



