148 VETERINARY BACTERIOLOGY 



ship between an antigen and its specific antibody. The serum 

 of a glandered animal is homologous for the glanders bacillus, but 

 is heterologous for the typhoid bacillus. 



Agglutinins are formed by the body for most foreign cells which 

 may enter or be injected. Red blood-cells, other body-cells, pro- 

 tozoa or bacteria, may be the antigens which provoke agglutinin 

 production. Under the right conditions the clumping will occur 

 whether the cells be living or dead, motile or non-motile. 



Agglutinogen. The antigen which causes the body to react and 

 produce agglutinins is called an agglutinogen. It is evident that 

 the agglutinogen is not the cell used for injection, but some sub- 

 stance produced by it. A culture of Bacillus typhosus in broth 

 may be passed through a porcelain filter, and the sterile filtrate 

 will still cause agglutinin production when injected into the animal 

 body. The agglutinogen is either something thrown off by the 

 antigenic cell in the process of growth, or formed as a result of 

 autolytic disintegration and digestion. Evidently some con- 

 stituent of the cell excites the production of the antibodies or 

 agglutinins, and these, therefore, unite with the corresponding 

 material in the bacterial or other cell. 



Ehrlich's Theory of Agglutinin Production. According to 

 Ehrlich, the agglutinogen unites with the receptors of the body- 

 cells, which are diverted in this way from their normal function. 

 As a result, there is an overproduction of the receptors and they 

 are freed as agglutinins. These freed receptors or agglutinins 

 differ in several ways from the antitoxins, for they not only com- 

 bine with the antigen, but they bring about certain changes in it. 

 Such receptors, to differentiate them from antitoxins and similar 

 antibodies (receptors of the first order), are termed receptors of 

 the second order. 



Constitution of the Agglutinin. The agglutinin may be shown 

 to consist of two portions a binding group and an agglutinating 

 group. The presence of the binding group, or haptophore, may be 

 shown by mixing bacteria with a serum containing the specific 

 agglutinin, and centrifuging. The supernatant liquid will be 

 found to have lost its agglutinating power that is, the agglutinins 

 will all have united with the bacteria first added, and will be removed 

 thereby from solution. The agglutinating group of the agglutinin 



