Scientific Proceedings. 



(93) 29 



cultures grown in the i.$fo and 4^0 solutions were changed to a 

 less degree and agglutinated in dilutions up to 1 in 100 and 1 in 

 60 respectively, and continued to absorb agglutinins. The re- 

 covery of the capacity to be agglutinated was very slow in the 

 culture grown in the strongest serum solution, when it was from 

 time to time transplanted in fresh nutrient agar. The other cul- 

 tures recovered this characteristic more rapidly. 



The first culture, after growth for sixteen weeks, during which 

 it was transplanted forty -three times, agglutinated in dilutions up 

 to 1 in 200, and after twenty weeks in dilutions up to 1 in 400. 

 The culture grown in 4fo solution of serum agglutinated after 

 sixteen weeks in dilutions up to 1 in 500, and one in 1.5 ^'agglu- 

 tinated in dilutions up to 1 in 800. This diminution and final 

 almost complete lack of development of agglutinable substance in 

 bacteria grown in a serum rich in agglutinin and immune bodies 

 is interesting. It showed not only a rapid variation in bacteria of 

 essential characteristics, but also indicated a possible means of 

 adapting themselves to resist destruction in the living body, since 

 the bacteria which ceased to produce agglutinable substance and 

 probably, also, less substance with affinity for other antibodies, 

 might be considered less vulnerable to these substances. 



It is not certain that the agglutinin in the serum causes the 

 change in the bacteria, for solutions may agglutinate and still not 

 produce this effect. The fact has been noted that the horse serum 

 of animals not immunized has much the same effect on the cultures 

 as the immune serum. Although this suggests that the change is 

 not due to antibodies, it does not prove this, since the serum of a 

 horse before injections is rich in antibodies for the typhoid-colon 

 groups, due possibly to the passage of bacteria from the intestines 

 into the circulation. 



The author's explanation of the process is that there are sub- 

 stances in the serum which attack certain parts of the bacteria 

 such as the agglutinable substance. In the increase of bacteria in 

 the serum those which produce the least of these substances are 

 least inhibited and therefore develop most rapidly. When cul- 

 tures are made from serum solution to serum solution daily, a 

 gradual differentiation takes place until finally bacteria producing 

 almost no agglutinable substance develop. 



