ANTIBODIES 119 



circulates until it reaches the sensitive cells. When 

 receptors are not present the animal possesses 

 natural immunity ; when they are present the organ 

 or body is more or less sensitive to the poison, and 

 antibodies are formed.* 



According to the views of Ehrlich, antibodies are 

 purely and simply receptors fitted for union with 

 the poison ; that when antitoxin is used therapeuti- 

 cally we are merely injecting a number of receptors 

 which will reinforce those of the organism. The 

 toxins are anchored to such receptors by the hapto- 

 phore group ; and when they have anchored the 

 toxin, the work of the receptors, as such, is done. 



All antibodies act in a similar way. But they 

 have another action upon the anchored substance. 

 This action may be direct, as in the case of the pre- 

 cipitins and agglutinins. It may, however, be in- 

 direct, as in the case of the opsonins, which render 

 the bacterial cells assimilable by phagocytes. 



There is another class of antibodies called by 

 Ehrlich the amboceptors. They are present in the 

 blood serum of normal animals, and are of various 

 kinds. They are considered by Ehrlich to play an 

 important role even in the normal condition. " I 

 hold that this function in physiological life is that 

 of seizing upon and elaborating nutritive sub- 

 stances.'^ They also arise as a new formation 

 during the process of immunisation. J They are 

 characterised by monotropism, and their presence 

 renders the cell liable to the action of a toxin-like 



* EhrlicK: "The Harben Lectures," Jour. Eoy. Inst. Pub. 

 Health, p. 326. 



Loc. cit. Loc. cit. 



