248 



ANTITOXINS 



used as an index of the reaction and subsequent doses. With the living 

 bacilli the doses injected on each of three days in succession are four, 

 ten, and thirty loopfuls suspended in salt solution. Flexner and Shiga 

 bacilli are inoculated alternately on three successive days, with inter- 

 vening rest intervals of seven days, the doses being chosen so as to pro- 

 duce a sharp febrile reaction which subsides in twenty-four hours. At 

 the end of eight to ten weeks' immunization the serum contains immune 

 agglutinins and a well-marked degree of antibacterial and antitoxic 

 value. 



Collecting and Testing the Serum. After three or four months a 

 trial bleeding should be made and the serum tested as follows : the mini- 

 mal lethal dose of a culture is determined and ten times this amount 

 placed in a series of tubes or syringes with increasing doses of serum; 

 the total quantity of injection is made up to 4 c.c. with sterile salt solu- 

 tion. The mixtures are set aside for one hour at 35 C. and injected in- 

 travenously in young rabbits. The animals are to be observed for at 

 least five days for diarrhea, paralysis, and loss in weight. For determin- 

 ing the antitoxic value a toxin is prepared by cultivating the bacilli 

 in sugar-free broth containing calcium carbonate for three days; the 

 bacilli are then killed with ether; the ether is removed and the culture 

 filtered through hard paper or a Berkefeld filter and the toxin kept in 

 the refrigerator. 



TABLE 4. METHOD OF TESTING ANTIDYSENTERIC SERUM (KRUSE- 



SHIGA) 



In this instance 0.004 c.c. of serum was sufficient to protect young 

 rabbits against 10 fatal doses of culture, and demonstrated that it is 

 possible to secure a fairly potent serum against the toxins of the Kruse- 

 Shiga microorganism. 



According to Todd, if the antiserum is given at least one-half hour 

 after administering the culture, it will protect the rabbit. If given 

 twenty-four hours later, it affords no protection. Similarly, the mix- 

 tures of culture and serum must not be injected immediately after mix- 



