448 MICROBIOLOGY 



bouillon but it will not clump other bacteria. The phenomenon 

 of agglutination therefore is a specific combination between the 

 agglutinin and the agglutinin-stimulating substance or ag- 

 glutinogen. It is very probable that the process follows certain 

 chemical laws, as definite quantitative relations exist between 

 the agglutinogen and the agglutinins so that the agglutination 

 reaction will vary in different tests in its degree of complete- 

 ness with the quantities of agglutinin and agglutinogen pres- 

 ent. This requires that a certain uniformity in the density and 

 quantity of the culture used should be maintained. Although 

 the agglutination test is specific there are groups of bacteria 

 that may be agglutinated by the serum containing the aggla- 

 tinin resulting from a single culture in the group. Whenever 

 an immune serum agglutinates a number of members of the 

 group closely related to the specific organism used for its pro- 

 duction, the reaction is spoken of as "group agglutination." 



The agglutinins are stable substances that resist drying 

 and can be kept dry and active for years. Widal and Sicard 

 found that they pass with difficulty through a porcelain filter 

 and do not dialyze. They are precipitated in part by 15 per 

 cent sodium chloride, which throws down fibrinogen, and 

 further precipitated with magnesium sulphate, which throws 

 down globulins. It is thought that they are intimately related' 

 to the globulins and to fibrinogen. A temperature of 60 C. 

 diminishes their activity, but some of them are not destroyed 

 "below 70 C. Sunlight has no effect upon them. 



Smith 14 has shown that there are two kinds of agglutinins 

 produced with certain motile bacteria, one of which acts upon 

 the bacteria directly, the other upon the fiagella. The occur- 

 rence of these two bodies, explains some of the incompatible 

 results of earlier experiments. 



The practical application of the agglutination test may be 

 made for diagnosis in any infectious bacterial disease if the 

 etiological organism is at hand, or the test may be made for the 

 "Smith. Jour. Med. Research, Vol. XII (1904). 



