716 MICROBIOLOGY OF DISEASES OF MAN AND DOMESTIC ANIMALS 



tinogens are combined together a new substance is formed which is 

 designated as an agglutinate. As to the location within the bacterial 

 cell of this agglutinogen (agglutinum) there is some dispute. Various 

 authorities have stated that it is present in the cell wall or on the cell 

 wall. Others have held the view that it is located within the cell proto- 

 plasm and in certain instances in the flagella. Without doubt, in 

 certain cases this substance is excreted from the cell into the surround- 

 ing medium, as is shown by the fact that when nitrates 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 co agglutinins. For example, the serum of 

 the patient suffering from typhoid fever or of a person or an animal 

 immunized with B. typhosus will produce an agglutination first of B* 

 typhosus, but in addition, an agglutination of E. coli, B, paracoli, B. 

 paratyphosus, 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 Ehrlich'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 



