THE AGGLUTININS 215 



difficulty, but further research has shown it to be full of com- 

 plexities. We will glance briefly at some more recent researches 

 on the subject, the exact explanation and significance of which 

 are not ascertained beyond dispute. 



Several facts go to show that the agglutinin of B. typhosus is not 

 a simple substance, but that two or more bodies are concerned. 

 (It may be mentioned that this bacillus has been studied more 

 than any other in this connection.) Thus Joos, after a series of 

 ingenious researches, came to the conclusion that the bacillus 

 contains two agglutinogens, and that each has its corresponding 

 agglutinin. The agglutinogen which is present in largest amount 

 (and which he calls a) is thermolabile, being destroyed at 62 C., 

 leaving only agglutinogen /3, which is thermostable. An animal 

 injected with living cultures will contain agglutinins (a and /3) 

 against both the substances. The first will combine with agglu- 

 tinogen a only, whilst the second will combine with both substances. 

 The two substances differ in their thermostability : a is thermo- 

 stable, but /3 loses its power of agglutination at 62 C. A couple 

 of examples of the facts which this complicated theory was intro- 

 duced to explain may be given. The serum of a horse treated 

 with living typhoid bacilli (and therefore containing agglu- 

 tinins a and /3) clumped a living culture at i : 20,000, and a 

 heated one at i : 1,000. When the supernatant fluid of this last 

 dilution was tested with heated typhoid bacilli, no agglutination 

 took place (agglutinin /3 had been removed), whereas it would 

 clump living bacilli readily enough. Agglutinin a was present in 

 larger amount than /3, and had not all been removed at this 

 dilution. Again, when heated serum is added to heated bacilli 

 there is no agglutination, since the thermolabile agglutinin /3 is 

 destroyed. The agglutinin a, it is true, is not destroyed, but its 

 agglutinogen (which is thermolabile) is. But when living bacilli 

 are now added clumping occurs, since the agglutinin a can find 

 unaltered agglutinogen a to affect. 



Smith and Reagh (and their researches have been, in the main, 

 corroborated by others) found that typhoid bacilli and other 

 flagellated bacilli might form two agglutinins the one acting 

 on the agglutinogen of the bodies of the bacilli, the other on that 

 of the flagella. The subject has also been investigated in a some- 

 what similar way by Buxton and Torrey, who find also two 

 agglutinins the one to a substance which remains attached to the 

 body of the bacillus, whilst the other can be separated from it by 



