BACILLUS ANTHRACIS. 
793 
successive generations in aqueous humour, and finding that 
the results appeared to vary considerably with the stage of 
the cultivation, those furthest removed from the original 
parent-source being more frequently inactive, he was led to 
make a series of observations, of which he now communicates 
the results. They may be stated as follows : 
That when Bacillus anthracis is artifically grown in succes¬ 
sive generations in a nutrient fluid (aqueous humour), it 
maintains its morbific properties through a certain number 
of generations, but each successive generation becomes less 
virulent than its predecessor, requiring both a longer time 
and a larger quantity to exert its morbific action; and after 
continuous diminution of virulence, at a certain stage in the 
successive cultivations, the Bacillus , though maintaining 
all its morphological characters and its power of growth, 
becomes completely innocuous even to the most susceptible 
class of animals. 
It may be added that the modified virus produces forms of 
modified disease which differ widely from ordinary splenic 
fever, both in the distribution of the Bacilli , and in the 
nature of the symptoms and pathological appearances. 
In regard to the general method employed in the determi¬ 
nation of the gradual diminution of virulence by successive 
artificial cultivations, the cultivating fluid was aqueous 
humour in closed tubes half filled, and the animals inocu¬ 
lated chiefly mice. The cultivations were continued to 
the nineteenth generation, each successive generation pre¬ 
senting identical morphological characters at the various 
stages of its growth, and showing no diminution in the 
capacity for growth nor marked variation in the time and 
temperature relations of its germination. In no case were 
any symptoms or a fatal result produced by inoculation with 
a later generation than the twelfth; beyond that stage, a 
large quantity of actively germinating rods and spores pro¬ 
duced no result whatever. The diminution of virulence was 
very marked at the eight generation, both as regards the pro¬ 
portion of animals affected and the rapidity of action with an 
equal dose. 
The author defers at present dwelling upon any conclusions 
to be drawn from the experiments pending further investiga¬ 
tions.— Bourn. of Roy. Mic. Society. 
