ACID AGGLUTINATION 283 



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- I/ 

 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. for thirty minutes 

 and lose their power only when heated to higher temperatures. It is 

 possible, therefore, to make a serum bacteriolytically inactive by de- K 

 stroying complement at 55 C., and still retain its agglutinating power. 



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

 state. They do not dialyze through animal membranes. 



(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. 



Acid Agglutination. Bacteria may be agglutinated by acids, and 

 the method of acid agglutination was introduced by Michaelis 1 for the 

 differentiation of bacterial species on the basis that the hydrogen ion 

 concentration at which agglutination is maximal is characteristic for 

 various species of closely allied types. The results of considerable 

 investigation on the acid-agglutination of the typhoid-colon group of 

 bacilli has shown that Bacillus typhosus and Bacillus paratyphosus are 

 readily distinguished by means of the reaction. Definite differentiation 

 between the paratyphoid bacilli A, B, and C have not been seen by 

 Beniasch, 2 Jaffe, 3 Heinmann, 4 and Grote 5 ; Beniasch has also reported 



1 Deutsch. med. Wochenschr., 1911, 37, 969. 



2 Ztsch. f. Immunitatsf., brig., 1912, 12, 268. 3 Arch. f. Hyg., 1912, 76, 1. 

 4 Ztsch. f. Immunitatsf., orig., 1913, 16, 127. 



5 Centralb. f. Bakteriol., etc., orig., 1913, 69, 98. 



