66 o. isHn 



9. The microscopic is more reliable than the macroscopic 

 method for weak or graphical agglutination work ; with strongly 

 agglutinating sera showing the same reactions in both, the macro- 

 scopic method is preferred, because it is easier and quicker than 

 the microscopic method. Therefore the macroscopic method is 

 to be regarded as most satisfactory for usual work and particularly 

 when many reactions are to be performed. 



10. Weak agglutination results if bacilli are heated at a tem- 

 perature of 45 to 55°C. for two to three hours; this temperature 

 does not affect the agglutinating activity of serum. Room 

 temperature and 37°C., both gave better results than higher 

 temperatures for the incubation of tests. 



11. Two to three hours are not enough for complete agglu- 

 tination; the tests should be set aside and read the next day. 



12. Normal horse serum showed strong agglutination reaction 

 with Bad. dysenteriae, Bad. coli and other bacilli of the tj^ihoid- 

 colon group. 



Polyvalent Bad. dysenteriae serum had strong agglutinating 

 power for Bad. typhosum and Bad. coli as well as for the dysentery 

 group. 



13. In serum diagnosis with the Widal test, many different 

 strains should be used since from one strain alone, rehable re- 

 sults cannot be obtained. 



SUPPLEMENTARY NOTES 



a. Eighteen to twenty-four hours cultures of the majority of 

 strains of Bad. coli grown at 37°C., show a tendency to spon- 

 taneous agglutination in most culture media; cultures growTi at 

 room temperature show less and are therefore preferable. 



b. Old stock cultures transplanted to a fresh culture medium 

 at first show weak, or no, susceptibility to agglutination; how- 

 ever, after a few sub-cultures (once or twice a day, if actively 

 growing bacilli), they regain this property. The same holds 

 good for all cultures of new bacilli, and it is necessarj^ therefore, 

 for accurate agglutination work to test the agglutiuabihty of 

 the bacterial culture with a control serum of known agglutinat- 

 ing powers. 



