470 



PATHOGENIC M1CROOI GANISMS 



used should be so great that 0.000001 c.c. of an 18-hour broth culture 

 will kill a mouse in 48 hours. Broth dilutions are then prepared in 

 such a. way that 0.5 c.c. of each dilution contains varying quantities of 

 the pneumococcus culture ranging from 0.2 c.c. to 0.0000001 c.c. 

 These dilutions should be freshly .made in order that the number of 

 organisms in the tube shall not be materially changed by growth or 

 death before the tests are made. With each of these dilutions, then, 

 0.2 c.c. of the serum to be tested is mixed in a syringe and the mixture 

 immediately injected intraperitoneally into the abdominal wall just 

 above the groin. In some laboratories the amount of serum used for 

 these standard tests is 0.1 instead of 0.2 c.c. The following is a typical 

 protocol taken from a protection experiment by Dochez and A very, 

 which illustrates the method: 



(The quantities in 

 cultures.) 



representing dose of culture refer to 18 hour broth 



The rule laid down for sera by Cole and his co-workers is that 

 only sera should be employed which in doses of 0.2 c.c. protects against 

 doses of 0.1 c.c. of a culture of the above description. Variations in 

 these standards are set up in other laboratories, and constant changes 

 are taking place in this phase of the work, but the above will suf- 

 ficiently illustrate the principle applied. 



Methods of Serum Treatment and Results. Hope of success with 

 serum treatment depends upon early diagnosis and immediate unde- 

 layed typing of the organism, since, as we shall see, the type I serum 

 alone is at the present time thought by everyone to exert definite 

 beneficial action. 



