CYTOLYSINS 149 



active immune serum shows the same inhibition zones and also simplified 

 the method. By allowing the original tubes to incubate twenty-four 

 hours at 37 C, the degree of clouding of the medium by bacterial 

 growth gives an excellent indication of the degree of bacteriolysis. He 

 found that normal rabbit serum shows bacteriolytic powers in strong 

 concentration, gradually diminishing as dilution proceeds. Thus the 

 low titer normal amboceptor fails to show inhibition zones, as is true 

 of low titer agglutinins and precipitins. A protocol from Buxton's 

 work shows the difference in activity of normal serum and immune 

 serum as well as the correspondence between the results of plating and 

 observation of original tubes. 



BUXTON EXPERIMENT 



Dilution Count of colonies on plates Observation of original tubes 



of sera Normal serum Immune serum Normal serum Immune serum 



i o Many thousand Clear Cloudy 



-2 o Many thousand Clear Cloudy 



-5 2 Many thousand Clear Clear 



-20 2500 4-5000 Cloudy Clear 



-40 Many thousand 4-5000 Cloudy Clear 



-80 Many thousand Many thousand Cloudy Cloudy 



-100 Many thousand Many thousand Cloudy Cloudy 



Teague and McWilliams have confirmed the work of Buxton and 

 others showing that normal rabbit serum is capable of killing large 

 numbers of typhoid and paratyphoid bacilli, but that the sera of rabbits 

 highly immunized against these organisms do not kill these bacilli. 

 These investigators have emphasized further that the normal bacteri- 

 olytic activity of rabbit serum for typhoid and paratyphoid bacilli is 

 not materially altered by immunization. In human typhoid fever the 

 blood serum normally shows bacteriolytic activity, but in spite of this bac- 

 teria multiply in the tissues apparently because the lymph does not pos- 

 sess bacteriolytic powers. Stone more recently made similar observations 

 but found further that fresh immune typhoid serum in vivo has appar- 

 ently a high bactericidal power, while fresh normal serum in vivo 

 has no protective power. Typhoid bacilli disappear more quickly from 

 the organs of immune animals than from normal animals, but macerated 

 organs from immune animals, cut sections, or their extracts are not 

 bactericidal even on the addition of fresh immune serum. This work 

 indicates that the destruction of typhoid bacilli in the immune animal 

 is due to some interaction between the tissue cells and plasma in vivo 

 or other unknown factor. 



The Bioscopic Method for Bacteriolysis. Neisser and Wechsberg 

 also devised the so-called bioscopic method of studying bacteriolysis. 

 They took advantage of the fact that living cells possess the power of 

 converting methylene blue into its colorless leucobase. By careful 

 adjustment of the number of bacteria it was possible to mix the various 

 agents together, add a very dilute alcoholic solution of methylene blue, 

 cover with paraffin and incubate. The degree of decolorization indi- 

 cates the relative amount of bacterial growth. 



Summary of Cytolysis. In summary it may be said that the phe- 



