40 CLINICAL BACTERIOLOGY. 



most evident in the case of the purely toxic bacteria. 

 If 0.5 cu. cm. of a tetanus bouillon-culture of deter- 

 mined toxicity are necessary to cause the death of a rab- 

 bit, 0.3 cu. cm. may perhaps induce passing rigidity, and 

 the introduction of o. I cu. cm. will be unattended with any 

 result ; and if o.ooooi cu. cm. of another culture will cause 

 the death of a white mouse, 0.000005 cu - cm - mav possibly 

 cause transitory mild tetanus, and o.oooooi cu. cm. no dis- 

 ease whatever. The greater or smaller number of bacteria 

 may in this case play no part in the result, but the larger 

 amount maybe fatal because with the larger number of bac- 

 teria a larger amount of already prepared toxin also is intro- 

 duced.; the smaller amount of toxin, however, which the 

 smaller number of bacteria carry with them, is readily with- 

 stood. With the infectious bacteria, also, a certain amount 

 of the infecting material is necessary to induce infection. For 

 dogs, highly virulent pneumococci injected subcutaneously 

 are in marked degree infectious ; they multiply rapidly, giv- 

 ing rise to extensive inflammation in the subcutaneous tis- 

 sues, and they cause death without septicemia, however. 

 When the virulence of the culture is sufficiently intense, 

 large dogs may be destroyed by as little as 0.5 cu. cm. of 

 the pneumococcus-culture. There thus results a true infec- 

 tion, and the possibility of a purely toxic action may safely be 

 excluded. From o. I to 0.3 cu. cm. of the same culture, 

 on the other hand, fail to induce any disease whatever in 

 the dog. The significance of the amount of the infecting 

 material is more questionable in the case of those bacteria 

 that give rise to septicemia. If pneumococci, which readily 

 cause fatal septicemia in rabbits, are introduced into the cir- 

 culation of these animals in great dilution, infection does not 

 take place. On the other hand, according to some observ- 

 ers, in the case of the septicemia of white mice and of an- 

 thrax of guinea-pigs, a single bacillus, presupposing the 

 virulence of the culture to be sufficiently great, may be ade- 

 quate to induce infection. This, however, appears question- 

 able, although it has been demonstrated that the individual 

 bacillus also in these two instances does not necessarily 

 cause infection, and that even one or two, or as many as ten, 

 of the most virulent anthrax-bacteria of the guinea-pig may 

 be borne without causing appreciable disease. That the 

 amount of the infecting material is also of significance in the 

 case of these bacteria endowed with especial virulence is 



