13 227 



Most of Ihe previous workers on this subject agree in giving another explana- 

 tion of this occurrence: thus Levin, working with B. coli, supposes that the dimin- 

 ished agglutinability is due to a destruction "— by the heating a great deal of the 

 agglulinable matter in the bacteria is destroyed". Eisenberg & Volk found that 

 B. typhosus, after heating to 100°, almost entirely lost its capacity for being agglut- 

 inated, while it preserved almost entirely its power of combining with the agglut- 

 inine. They explain this by assuming that the labile agglutinophore group of the 

 bacteria is destroyed, while the stable group that unites the agglutinine to the 

 bacteria is far less easily injured by the action of heat. Thus they draw a close 

 parallel between the facts here and the discoveries made by Ehulich with reference 

 to diphtheria toxine. 



But OUT researches with B. coli argue entirely against the view that the diminu- 

 tion of agglutinability depends upon a destruction of the agglulinable substance of the 

 bacteria. For if it were here a question of an actual destruction or weakening, 

 comparable to that which has been described in connection with the various 

 bacterial toxines, it is evident that longer continuation of the heating at anj' given 

 temperature could only result in a further loss of agglutinability, which would 

 finally be complete. This however does not take place; the researches set down in 

 Tables VIII and IX shew that in this matter, as in others, the results obtained vary 

 according as use is made of a bouillon-culture or an agar-culture suspension. 



If an agar-culture suspension of B. coli is warmed to 70° for various lengths 

 of time — for from 1 to 75 minutes — in certain cases (see Table VIII) the agglut- 

 inability diminishes more and more the longer the heating is continued — see 

 Series 33. Yet in other instances, such as Series 36, the loss in agglutinability is 

 practically uniform ; and in yet others, continued heating even makes the suspension 

 more easily agglutinated than it was originally — see Series 37. But when a 

 bouillon-culture is heated, to say 70°, as in Table IX, Series 38 to 42, the diminu- 

 tion in agglutinability is much the same whether the heating is continued for a 

 long time or for a short. 



Again, where an agar-culture suspension of B. coli is heated to 100° for |)eriods 

 of from 1 minute to 5 hours — see Table X — it appears that continued heating 

 gradually restores the agglutinability of the bacteria, so that in some cases it finally 

 happens that they recover their agglutinability entirely. It is not easy to under- 

 stand why the same stock of B. coli should give such varying results at different 

 times, when no change is made in the immune-serum employed; the experiments 

 in Series 43 to 46 were made with one serum, those in Series 47 to 50 with another. 



As regards the effect of the heating of bouillon-cultures to 100° for different 

 lengths of time, the figures in Series 51 shew that the loss of agglutinability 

 remains the same throughout. But if f/o of formaldehyde be added to the culture 

 before it is warmed, then, as the experiments of Series 52 shew, protracted warming 

 causes a partial return of the agglutinability. 



