182 



PRINCIPLES OF BACTERIOLOGY 



infection. Suppose, for instance, the serum from a typhoid case agglu- 

 tinates both the laboratory cultures of the typhoid bacilli and those 

 of a variety of the colon group. We saturate the serum with typhoid 

 bacilli. If the serum loses its agglutinating power for the typhoid 

 bacillus only, it is a case of mixed infection with both the typhoid 

 bacillus and the type of colon bacillus used in the test. If the 

 serum loses its agglutination for both the B. typhi and the B. coli, 

 then it is a pure typhoid infection, the B. coli having been agglu- 

 tinated by the group-agglutinins produced because of the typhoid 

 infection. 



The conclusions Castellani derived from the facts stated in para- 

 graphs 1 and 2 are not warranted, because of the fact that bacteria 

 absorb group agglutinins produced by other varieties of bacteria and 

 which agglutinins may not appreciably affect them. The agglutinins 

 in the serum of the supposed case of typhoid fever which agglutinated 

 the test culture of B. coli and were absorbed by B. typhi were not, it 

 is true, produced by the variety of B. coli of the test culture, but they 

 may have been produced, and in fact probably were, by some other 

 variety of B. coli. The B. typhi is less apt to produce abundant group 

 agglutinins for B. coli than are other varieties of B. coli, and it absorbs 

 the group agglutinins produced by many varieties of the B. coli for 

 other bacteria. 



The results of a number of experiments carried out by us demon- 

 strate this. The following tables give the outcome of several experi- 

 ments : 



ABSORPTION BY THE TYPHOID BACILLUS OF GROUP AGGLUTININS ACTING UPON A 



NUMBER OF VARIETIES OF B. COLI WHICH WERE PRODUCED BY 



ANOTHER VARIETY OF B. COLI. 



Agglutination by Serum of Rabbit Immunized to Colon Bacillus X. 



After attempt at absorption 

 with typhoid bacilli at 22 C. 

 600 

 20 

 80 

 30 

 10 



less than 10 

 <. .< 10 



10 



The absorption tests were carried out by adding the bacilli from 

 recent agar cultures to a 10 per cent, solution of the serum in a twenty- 

 four-hour bouillon culture. The mixture was allowed to stand for 

 twenty-four hours at about 22 C. It was found that a simple dilution 

 of serum when left at 37 C. rapidly deteriorated. Thus, in an extreme 

 instance a serum positive at 1 : 1500, when diluted with bouillon or 

 salt solution 1 : 25 and left at 37 C. for twenty-four hours, lost 30 to 

 40 per cent, of its strength; at 22 C. it lost 15 to 20 per cent. Left for 

 three hours only, the loss was only 5 to 10 per cent. 



