7l6 MICROBIOLOGY OF DISEASES OF MAN AND DOMESTIC ANIMALS 



ing medium, as is shown by the fact that when filtrates of bacterial cul- 

 tures are injected they frequently give rise to the formation of agglu- 

 tinins. This agglutinogenic substance is specific and varies with the 

 species. There are, however, very closely related substances of this 

 character among some groups of bacteria. When these agglutinogenic 

 substances are injected into the animal they frequently give rise to 

 agglutinins which when combined with other members of this group 

 will produce agglutination in low dilutions. Such a reaction and prop- 

 erty is known as "group agglutination," and the agglutinins produced 

 in such a case are known as coagglutinins. For example, the serum of 

 the patient suffering from typhoid fever or of an animal immunized 

 with B. typhosus will produce an agglutination first of B. typhosus, but 

 in addition, an agglutination of B. coli, B. paracoli, B. paratypkosus, 

 and B. enteriditis. The agglutination of these last-named organisms, 

 of course, will not be active except in low dilutions, and in order to 

 exclude them satisfactorily it- is necessary to dilute the serum to a 

 higher point. This phenomena of coagglutination is due to the fact 

 that there are some chemical substances (agglutinogenic) within these 

 bacteria which are common to all and which give rise to the formation 

 of agglutinins, which are chemically similar to each other in certain 

 respects. 



Structure of Agglutinins and Agglutinogens. — According to EhrUch's 

 conception the agglutinins are composed of two chemical groups, a 

 haptophile or combining group with which it combines with the hapto- 

 phore group of the agglutinogen and a zymophorous or agglutinophor- 

 ous group which actually produces the agglutination. The agglutino- 

 gen is also composed of a combining group known as the haptophore 

 group with which it combines with haptophile of the agglutinin. It is 

 probable that this same haptophore group will combine also with vari- 

 ous tissue cells and give rise to formations of agglutinins which are really 

 free haptophile receptors of the tissue cells which have been acted upon 

 by the agglutinogenic substance contained in the bacteria. 



Agglutinoids. — It is possible by means of heat and chemicals to 

 destroy the zymophorous group of the agglutinin leaving only the hapto- 

 phile group. Such a substance is known as an agglutinoid, being similar 

 to a toxoid. A temperature of not to exceed 60° to 70° is necessary 

 to produce this substance. Agglutinoids will combine with the agglu- 

 tinogen of the bacteria but they will not produce a clumping or an agglu- 



