THE BIOLOGY OF MICROBES, ETC. 147 



invariably killed, though some animals survived it : 

 ^ cc. always caused an extensive abscess, of which 

 the animals usually died in six to eight weeks. 

 Doses of less than -g-J-^ cc. did not produce any 

 effect. We have thus three results, according to the 

 dose employed. A small dose (below -g-J^ cc.) pro- 

 duced no effect ; from -^ to -^ cc. caused abscesses, 

 while above ^V cc - caused death in from twenty- 

 four to thirty-six hours. Further, the size of the 

 abscess depended apparently also on the dose, -^ 

 cc. causing only a slight trace of pus, which dis- 

 appears, while T V causes a large and spreading 

 abscess, ultimately resulting in the death of the 

 animal; and the intermediate doses produce inter- 

 mediate effects. On several occasions I have diluted 

 the cultivation considerably, and made plate-cultiva- 

 tions from this diluted material, in order to ascertain 

 the number of bacteria present by counting the 

 number of colonies which developed. The result is 

 that on an average 1 cc. of gelatine cultivations 

 contained 4,500,000,000 bacteria. Thus, doses up 

 to 9,000,000 produced no effect; from 9,000,000 

 up to 112,500,000 caused abscesses, and above 

 225,000,000 caused death. It is difficult to under- 

 stand the influence of dose in producing these 

 effects, but the following seems to be a fair supposi- 

 tion. Eabbits are not very susceptible to the action 

 of this bacterium ; in other words, in the struggle 

 for existence between the bacteria and the cells 

 which follows the introduction of this bacterium, 

 the victory will, in most cases, remain with the 

 cells, and the bacteria will disappear. If, however, 



