228 14 



As an explanation of this diminished aggUitinability, ive believe that some 

 portion of their contents is dissolved out of the bacteria in the process of heating their 

 suspension in normal saline, and that some substance that unites witli the agglulinine 

 is taken up by the fluid in which they float. 



We have proved that such a process does take place by filtering off the 

 bacteria from the fresh suspension, both before heating and after it, and have al- 

 ways found that the filtrate from the heated emulsion contained substances capable 

 of uniting with the agglutinine, while no such substance was present in the filtrate 

 from the unhealed suspension. And if fresh unhealed bacteria are emulsionised in 

 these two filtrates, it will be found that the bacteria suspended in the filtrate from 

 the heated emulsion require considerably more immune-serum for their agglutination 

 than do the bacteria suspended in the filtrate of the unhealed emulsion. 



The return of aggUitinability on prolonged heating at 100° may depend in 

 part upon the slow destruction of these substances that combine with the agglutinine, 

 or upon their conversion into substances that are indifferent to the agglutinine. 

 That some such processes occur is shewn by our experiments with the filtrate from 

 heated B. coli emulsions; on further prolonged heating to 100°, this filtrate entirely 

 lost its power of combining with agglulinine. But these considerations are not enough 

 to account for the very considerable lowering of agglutinabilitij caused by heat: some 

 other factor which still remains obscure, possibly a change in the surface-tension of 

 the bacterial envelope, must be at work as well. 



It might be urged, in opposition to the foregoing views as to the agglutination 

 of bacteria heated for long periods, that it is wholly different in character from 

 that of bacteria that have been heated for only a short time, or that have not been 

 heated at all, and is therefore, perhaps, not a specific reaction at all. But the evi- 

 dence for the specific nature of the agglutination produced by the serum is as good 

 in the one case as it is in the other; and, further, very similar phenomena have 

 been noted by Dreyeiî in the case of a megatheriolysine. 



This lysine, on being warmed to 60° for half an hour, was found to lose its 

 power of haemolysing red blood-corpuscles; but if the same lysine-solution were 

 then warmed to 100° for 10 minutes, it recovered a portion — perhaps a quarter — 

 of its original haemolytic power. If the lysine be heated directly up to 100°, its 

 power is reduced to Vs of what it was originally; while if it be kept at 100° for 

 10 minutes, its activity partially returns, and it may be found to have half of its 

 original power of haemolysing red cells. Here again, it might be argued that the 

 megatheriolysine thus reactivised by heal is not identical witii that originally pre- 

 sent; but no such dill'erence really exists between the two, because the specific anti- 

 megatheriolysine is able to prevent haemolysis by the megatheriolysine healed to 100°, 

 just as it does haemolysis by the unheutcd megatheriolysine. 



