270 AGGLUTININS 



In accordance with the side-chain theory, the ability of an animal to 

 form agglutinins for a certain microorganism would depend on its pos- 

 session of receptors of the second order, which are able to unite with the 

 agglutinogenic receptors of the microorganism. It has been well es- 

 tablished that the number of such suitable receptors vary in animals, and 

 that different animals may not produce serums with equal agglutinating 

 powers. 



Agglutinins do not appear in the serum immediately after inocula- 

 tion, but require an incubation period of from two to four days for their 

 production. 



Properties and Nature of Agglutinins. (1) Agglutinins are fairly 

 resistant substances that withstand heating to 60 C. and lose their 

 power only when heated to higher temperatures. It is possible, there- 

 fore, to make a serum bacteriolytically inactive by destroying comple- 

 ment at 55 C., and still retain its agglutinating power. 



(2) They resist drying, and their activity is best preserved in this 

 state. 



(3) They are precipitated from a serum by magnesium or ammonium 

 sulphates, when these salts are used in proper concentration, and are 

 thus closely associated with the globulin fraction of serum. 



(4) They are separate and distinct antibodies, and are not associated 

 with bacteriolysins. Thus the agglutinins of an immune serum may be 

 lost, destroyed, or absorbed and the bacteriolysins retained. As pre- 

 viously mentioned, the bacteriolytic power of a serum may be inhibited 

 by heating it to 55 C. for one-half hour without influencing the agglu- 

 tinin content, and during disease processes the formation of agglutinins 

 and that of bacteriolysins are apparently not parallel processes. 



Mechanism of Agglutination. The true nature of the phenomenon 

 of agglutination is unknown, as is shown by the number of theories ad- 

 vanced. Thus 



1. Gruber's idea of the mechanism of this phenomenon was that the 

 agglutinin so changed the bacterial membrane as to render it more 

 viscous, and that this increased viscosity caused the bacteria to adhere 

 and form clumps. No visible changes in the organisms or red corpuscles 

 can, however, be seen. 



2. Paltauf s theory is somewhat similar, he believing that the agglu- 

 tinogen is precipitated on the surface of the bacteria by union with the 

 agglutinin, with the formation of a sticky substance. He cites evidence 

 that tends to show that such substances are actually thrown out from 

 the bacteria during agglutination, as may be seen in a properly stained 



