Studies in Bacterial Variability. 



61 



the second of which constituted culture T.e. 9. This point is further 

 illustrated in a later experiment. 



So far there had been obtained from the culture T.e. cultures T.e. 5 and 

 T.e. 9, the former definitely dys-agglutinable,. the latter a good deal more 

 agglutinable than T.e., in fact, two and a half times as agglutinable when 

 referred to standard serum. 



3. Culture T.e. 9 produced in rabbit 3 a serum of very high agglutinating 

 power for T.e. and T.e. 9. This, however, does not indicate that in T.e. 9 one 

 has isolated a specially powerful antigenic form of the bacillus. It only 

 shows that rabbit 3 was a particularly good subject for the production of 

 agglutinins. For on looking at the serums obtained from rabbit 1, it is seen 

 that T.e. 9, which was used for the third inoculation, did not in this animal 

 cause any increase of T.e. agglutination above its previous level. 



On the other hand, it is very evident that T.e. 9 was remarkably poor in 

 antigenic power for the dys-agglutinable bacillus T.e. 5. For whereas 

 serum III (T.e. 9) was nine or ten times as powerful (24 hours readings) in 

 its action on T.e. 9 as serum I, 1 (T.e.), it was only about one-fifth as strong 

 against T.e. 5. That is to say that in culture T.e. 9 the antigenic power of 

 the original T.e. has been reduced to about one-fiftieth as concerns T.e. 5. 



4. Serum II (T.e. 5) is seen to be much more powerful in its action on 

 T.e. 5 culture than either of the other serums from single inoculations, and as 

 powerful (24 hours readings) as the serums I, 2 and I, 3, though these serums 

 act two or three times as strongly against cultures T.e. and T.e. 9 as does 

 serum II. Nevertheless, T.e. 5, which has become markedly dys-agglutinable, 

 still retains at .this stage good antigenic power in forming agglutinins for T.e. 



There is, however, some evidence that its antigenic power for T.e. has 

 undergone reduction, since though serum II (T.e. 5) is definitely stronger than 

 serum I, 1 (T.e.) for the original culture T.e. (say 16 per cent.), it was 

 perceptibly weaker in its action on culture T.e. 9 (say 7 per cent.). 



In view of the foregoing considerations, it would seem that by growing 

 the bacillus T.e. in agglutinating serum one was in process of separating out, 

 whether by the mechanical action of clamping and sedimentation alone, or 

 by this combined with an influence favourable to the preferential multiplica- 

 tion of the less agglutinable members of the population, a dys-agglutinable 

 form of the bacillus ; and that incidentally one also isolated a particularly 

 highly agglutinable form, T.e. 9. 



In this latter culture dys-agglutinable elements were much less well 

 represented than in the original T.e. from which both had been derived, as 

 shown by its feeble antigenic action in relation to culture T.e. 5, when used 

 for the production of agglutinating serum. But that they were by no means 



