1 64 LECTURES ON IMMUNITY 



occurs, and that normal serum or even dissolved starch 

 has a somewhat protecting influence against the agglutina- 

 tion. But later on M. Henri and Mme. Girard-Mangin 

 investigated the influence of negative colloids, and found 

 that they had precisely the same agglutinating influence 

 as the positive ones. The "colloidal theory," therefore, 

 has proved of little avail. 



That proteins are able to combine with positive ions, not 

 only hydrogen, but even potassium, sodium, or calcium, 

 has, according to the investigations of Pauli and Loeb, 1 an 

 extremely great importance for the physiological functions 

 of the proteins. 



We have seen in the chapter on the velocity of reaction 

 that this is for agglutinins proportional to the concentra- 

 tion of the agglutinin and increases with temperature. 

 From this we concluded that the agglutination depends on 

 a chemical reaction of the agglutinin with some content of 

 the bacterium. In his excellent work on microbiology 

 Duclaux 2 shows that this chemical action is really a coagu- 

 lation. He cites the experiments of Kraus, which indicate 

 that the filtrate obtained by means of a Chamberland filter 

 from cultures of cholera vibrios, typhoid or pest-plague 

 bacilli, give a coagulum with their specific agglutinins. He 

 cites further the experiments of Nicolle, who subjected a fil- 

 trate from macerated coli bacilli to an agglutinin obtained 

 by injecting these bacilli into the veins of a rabbit. In a 

 mixture of ten drops of the filtrate with one drop of the 

 rabbit's serum there appeared after some hours at 37 a 

 large number of flocculent bodies that resembled to a very 



1 J. Loeb : " Studies in General Physiology," Part II, 544, Chicago, 1905. 



2 Duclaux : "Traite de microbiologie," T. II, p. 706, Paris, 1899. 



