VI 



THE MODE OF PROCEEDING. 



As none of the earlier methods was exact enough 

 for our purpose, we performed the testing of the agglu- 

 tinating power by the macroscopic precipitation in test 

 tubes in the following manner. 



The culture of Bacillus typhosns, which served for 

 all our experiments, had been cultivated on artificial 

 media in the laboratory for several years and was only 

 slightly virulent. 5 cc. of a 24h broth culture injected 

 on rabbits, and KM) cc. injected on goats, produced only 

 a very slight illness, but was not at all able to kill the 

 animals. A very light and clear broth was used for 

 the culture, which was left 18 24 hours in the incu- 

 bator. It was then carefully examined as regards infec- 

 tion with other microbes, and afterwards formaldehyd 

 ' '/.-) /oo was added. This made it possible to keep the 

 culture in uncovered test tubes for some hours at 37 

 without being contaminated. 



A large series of test tubes was filled with exactly 

 the same quantity of this fluid. For our first experi- 

 ments 10 cc. were used, but it was often found more 

 practical to take only 1,5 cc. in thin test tubes (11 X 70 

 mm.), especially when only small quantities of serum 

 were at our disposal. 



When we had to lest and compare the agglutinating 

 power of for instance 12 different sera, then for each 

 test a series of such tubes was used and decreasing 

 amounts of the serum were distributed among them. 

 The tubes from all 12 tests having been thoroughly 

 shaked were at the same time placed alltogcther in an 

 Oslwald water incubator at 37 for about l l / z hour, 

 then at once taken out and examined. 



If suitable doses of serum were chosen, each series 

 will show a continuous scale of clarification, from com- 



